176. Sabal, MC; Boyce, MS; Charpentier, CL; Furey, NB; Luhring, TM; Martin, HW; Melnychuk, MC; Srygley, RB; Wagner, MC; Wirsing, AJ; Ydenberg, RC; Palkovacs, EP. (2021) Predation landscapes influence migratory prey ecology and evolution.Trends Ecol. Evol. 36: 737-749 Predation landscapes influence migratory prey ecology and evolution
Migratory prey experience spatially variable predation across their life cycle. They face unique challenges in navigating this predation landscape, which affects their perception of risk, antipredator responses, and resulting mortality. Variable and unfamiliar predator cues during migration can limit accurate perception of risk and migrants often rely on social information and learning to compensate. The energetic demands of migration constrain antipredator responses, often through context-dependent patterns. While migration can increase mortality, migrants employ diverse strategies to balance risks and rewards, including life history and antipredator responses. Humans interact frequently with migratory prey across space and alter both mortality risk and antipredator responses, which can scale up to affect migratory populations and should be considered in conservation and management. DOI PubMed
175. Walters, KE; Reynolds, JD; Ydenberg, RC. (2021) Ideal free eagles: Bald Eagle (Haliaeetus leucocephalus) distribution in relation to Pacific salmon (Oncorhynchus spp.) availability on four spawning rivers.Can. J. Zool. 99: 792-800 Ideal free eagles: Bald Eagle (Haliaeetus leucocephalus) distribution in relation to Pacific salmon (Oncorhynchus spp.) availability on four spawning rivers
Bald Eagles; Haliaeetus leucocephalus; Pacific salmonids; Oncorhynchus spp.; Ideal Free Distribution; resource patches; behavioural ecology; spatial distribution; scavengers; temporal distribution
The movement of individuals according to the availability of resources has a fundamental effect on animal distributions. In the Pacific Northwest, Bald Eagles (Haliaeetus leucocephalus (Linnaeus, 1766)) rely heavily on scavenging opportunities during the non-breeding period, and their distribution and movements are thought to be strongly influenced by the availability of post-spawning Pacific salmon (genus Oncorhynchus Suckley, 1861) carcasses. We surveyed the abundance of eagles and salmon on four adjacent rivers on Vancouver Island, British Columbia, Canada, during the 2017 fall spawning season. Salmon began to arrive in late September, peaked in abundance in mid-November, and were absent after early December. The seasonal progression of Bald Eagle abundance matched that of salmon carcass availability. The slope of proportional eagle-salmon relationship was significantly positive, though lower than the 1:1 match predicted by Ideal Free Distribution theory. The numerical response of Bald Eagles to salmon abundance was elevated on one of the rivers, potentially due to physical features such as sandbars and mudflats that increased the availability of carcasses and provided access points for eagles. DOI
173. Bos, D; van Loon, EE; Klop, E; Ydenberg, R. (2020) A Large-Scale Experiment to Evaluate Control of Invasive Muskrats.Wildl. Soc. Bull. 44: 314-322 A Large-Scale Experiment to Evaluate Control of Invasive Muskrats
catch-per-unit effort; management experiment; muskrat; Ondatra zibethicus; pest species; spatial context; The Netherlands; trapping
The muskrat (Ondatra zibethicus) is an invasive species in Europe. The extensive waterways of the Netherlands provide ideal habitat for muskrats, and a large population established itself after arrival in 1941. A control program was put into effect immediately because muskrat burrowing can compromise the integrity of dikes and, hence, poses a significant public safety risk. The current (2015) annual catch of approximately 89,000 individuals is equivalent to approximately 0.30 muskrats/km of waterway, well above the national objective in spite of decades of effort. The control program is expensive (euro35 M annually) and contested by animal rights groups. These factors created the need for a careful evaluation of the full range of control possibilities, from 'no control' to 'extermination.' As part of this, we experimentally evaluated the validity of a previously published correlation (based on historical data) between catch and effort. We raised or lowered removal effort (2013-2016) in a stratified random sample of 117 5-km x 5-km 'atlas squares' from the national grid. We found that catch-per-unit effort (CPUE) decreased after effort was increased, and rose after effort was decreased, by amounts slightly greater than expected based on the correlational data, though confidence intervals enclose zero. As anticipated, CPUE varied consistently and strongly between seasons. The biggest (and unanticipated) effects were those of the catch in the preceding 3 years ('history'), and surrounding area ('neighborhood'). Our experiment confirms estimates of intensity of control required to lower muskrat populations. These results will help with more effective allocation of control effort, and better-informed evaluation of the economic costs of various control options. (c) 2020 The Authors. Wildlife Society Bulletin published by Wiley Periodicals, Inc. on behalf of The Wildlife Society. DOI
172. de Jong, JF; van Hooft, P; Megens, HJ; Crooijmans, RPMA; de Groot, GA; Pemberton, JM; Huisman, J; Bartos, L; Iacolina, L; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2020) Fragmentation and Translocation Distort the Genetic Landscape of Ungulates: Red Deer in the Netherlands.Front. Ecol. Evol. 8 Fragmentation and Translocation Distort the Genetic Landscape of Ungulates: Red Deer in the Netherlands
red deer; ungulate; gene flow; translocation; single nucleotide polymorphisms; genetic monitoring
Many ungulate populations have a complex history of isolation and translocation. Consequently, ungulate populations may have experienced substantial reductions in the level of overall gene flow, yet simultaneously have augmented levels of long-distance gene flow. To investigate the effect of this dual anthropogenic effect on the genetic landscape of ungulates, we genotyped 35K SNPs in 47 red deer (Cervus elaphus) of Netherlands, including putative autochthonous relic populations as well as allochthonous populations established in private estates and rewilding areas. We applied F-ST and ordination analyses to determine the meta-population genetic structure and thereby the occurrence of hybridization. At population level, we investigated levels of inbreeding through individual-based diversity measures, including Runs of Homozygosity. We documented that both spatial genetic structure and within-population genetic variation differed markedly from patterns assumed from present-day abundance and distribution. Notwithstanding the small spatial scale, red deer populations formed distinct genetic clusters, and some had higher genetic similarity to distant than to nearby populations. Moreover, the putative autochthonous relic deer populations had much reduced levels of polymorphism and multi-locus heterozygosity, despite relatively large current population sizes. Accordingly, genomes of these deer contained a high proportion of long (>5 Mb) Runs of Homozygosity. Whereas the observed high levels of inbreeding warrant defragmentation measures, the presence of adjacent autochthonous and allochthonous genetic stocks imply that facilitation of gene flow would cause genetic homogenization. Such distortions of the genetic landscape of ungulates creates management dilemmas that cannot be properly anticipated without baseline genetic monitoring. DOI
171. Hope DD, Lank DB, Smith PA, Paquet J and Ydenberg RC. (2020) Migrant semipalmated sandpipers (Calidris pusilla) have over four decades steadily shifted towards safer stopover locations.Frontiers in Ecology and Evolution 8: 3 Migrant semipalmated sandpipers (Calidris pusilla) have over four decades steadily shifted towards safer stopover locations
Peregrine falcons (Falco peregrinus) have undergone a steady hemisphere-wide recovery since the ban on DDT in 1973, resulting in an ongoing increase in the level of danger posed for migrant birds, such as Arctic-breeding sandpipers. We anticipate that in response migrant semipalmated sandpipers (Calidris pusilla) have adjusted migratory behavior, including a shift in stopover site usage toward locations offering greater safety from falcon predation. We assessed semipalmated sandpiper stopover usage within the Atlantic Canada Shorebird Survey dataset. Based on 3,030 surveys (totalling ~32M birds) made during southward migration, 1974–2017, at 198 stopover locations, we assessed the spatial distribution of site usage in each year (with a “priority matching distribution” index, PMD) in relation to the size (intertidal area) and safety (proportion of a site's intertidal area further than 150 m of the shoreline) of each location. The PMD index value is >1 when usage is concentrated at dangerous locations, 1.0 when usage matches location size, and <1 when usage is concentrated at safer locations. A large majority of migrants were found at the safest sites in all years, however our analysis of the PMD demonstrated that the fraction using safer sites increased over time. In 1974, 80% of birds were found at the safest 20% of the sites, while in 2017, this had increased to 97%. A sensitivity analysis shows that the shift was made specifically toward safer (and not just larger) sites. The shift as measured by a PMD index decline cannot be accounted for by possible biases inherent in the data set. We conclude that the data support the prediction that increasing predator danger has induced a shift by southbound migrant semipalmated sandpipers to safer sites. DOI
170. Reiter, ME; Palacios, E; Eusse-Gonzalez, D; Gonzalez, RJ; Davidson, P; Bradley, DW; Clay, R; Strum, KM; Chu, J; Barbaree, BA; Hickey, CM; Lank, DB; Drever, M; Ydenberg, RC; Butler, R. (2020) A monitoring framework for assessing threats to nonbreeding shorebirds on the Pacific Coast of the Americas.Avian Conserv. Ecol. 15 A monitoring framework for assessing threats to nonbreeding shorebirds on the Pacific Coast of the Americas
conservation; habitat associations; hypothesized threats; monitoring network; Pacific Americas Flyway; shorebirds
Many shorebirds (Order: Charadriiformes; Family: Charadriidae, Recurvirostridae, Scolopacidae, Haematopodidae, Jacanidae) are highly migratory, traversing thousands of kilometers between high latitude breeding and low latitude nonbreeding sites. In doing so, they are dependent on networks of coastal and interior wetland ecosystems. To aid in the effective conservation and management of their populations, and to assess the impact of threats facing shorebirds, standardized data on shorebird abundance are needed from multiple sites representing a gradient of conditions across the hemisphere. Such data would provide insight on whether fluctuations at one location represent real changes in abundance because of some localized threat, or whether other factors acting across broader scales such as the redistribution of predators, are responsible. We designed the Migratory Shorebird Project (MSP), now implemented in 11 countries along the Pacific Coast of the Americas, to characterize spatial and temporal variation in shorebird abundance, to understand which factors (habitat, threats) most influence their populations across the flyway, and to increase capacity for integrated research, monitoring, and conservation. We used bird inventory data from historical surveys and spatial data on habitat distribution along with a set of hypotheses about important threats to guide the design of the project and to identify data requirements to test hypotheses. We counted birds one time per year at 84 nonbreeding sites (similar to 1400 sampling units) between 15 November and 15 February, when shorebirds were relatively stationary. In each of the first three annual counts from 2013/14 to 2015/16, the Migratory Shorebird Project counted similar to 1M shorebirds representing 44 species, including five species for which > 20% of the estimated biogeographic population was recorded annually, and nine additional species with > 5% recorded annually. The magnitude of variability in estimates of shorebird abundance was inversely correlated with survey effort with the most uncertainty, and lowest survey effort, in the South Temperate region followed by the Neotropical region (southern Mexico to northern Peru) and then the North Temperate region. Evaluation of variance highlighted both among-site and among-unit ("units" are nested within sites) variation in bird abundance and cover types as well as threats such as potential disturbance and predator abundance. Overall, shorebird density was significantly, and positively, associated with the area (ha) of intertidal mudflats, beaches, and aquaculture. Survey units with intermediate levels of bare ground and flooding had the highest shorebird density. As for threats, we found, contrary to our hypothesis, that shorebird abundance was significantly, and positively, associated, with the density of Peregrine Falcons (Falco peregrinus); however we found no relationship between shorebird abundance and the amount of urban development, our index to potential human disturbance, in the surrounding landscape. The Migratory Shorebird Project is providing an essential data foundation and network for increased knowledge of the factors affecting shorebirds across the Pacific Coast of the Americas and identifying what and where conservation actions could have the greatest impact. DOI
169. Tavera, EA; Stauffer, GE; Lank, DB; Ydenberg, RC. (2020) Oversummering juvenile and adult Semipalmated sandpipers in Peru gain enough survival to compensate for foregone breeding opportunity.Mov. Ecol. 8 Oversummering juvenile and adult Semipalmated sandpipers in Peru gain enough survival to compensate for foregone breeding opportunity
Calidris pusilla; Oversummering; Survivorship; Multi-state mark-recapture model; Migratory strategy; Distance-dependant; Shorebirds; Paracas; Peru
Background: Age at maturity and the timing of first breeding are important life history traits. Most small shorebird species mature and breed as 'yearlings', but have lower reproductive success than adults. In some species, yearlings may defer northward migration and remain in non-breeding regions ('oversummering') until they reach 2 years of age. Some adults also oversummer. Oversummering would be favoured by natural selection if survival were as a result raised sufficiently to compensate for the missed breeding opportunity. Several thousand Semipalmated Sandpipers (Calidris pusilla) spend the non-breeding period at Paracas, Peru, including individuals with long bills (likely from eastern Arctic breeding populations similar to 8000 km distant) and short bills (likely from western Arctic breeding populations, up to 11,000 km distant), with short-billed birds more likely to oversummer. We tested the prediction that oversummering birds have higher survival than migrants, and that the magnitude of this higher survival for oversummering birds is enough to compensate for their lost breeding season. Methods: We used a Multi-State Mark-Recapture model based on 5 years of encounter data (n = 1963 marked birds, and 3229 resightings) obtained year-round at Paracas, Peru, to estimate seasonal (i.e. breeding and non-breeding) survivorship for migrant and oversummering birds. We calculated the magnitude of the oversummering survival advantage required to compensate, for both yearlings and adults, based on published measures of annual survival and reproductive success. Using bill length as a proxy for migration distance, we investigated whether migratory survival is distance-dependent. Results: We estimate that 28% of yearlings and 19% of adults oversummer. Survival is higher for oversummering birds than for migrants, and the oversummering survival advantage is greater for adults (0.215) than for yearlings (0.140). The theoretical thresholds predicted by the size of the missed reproductive opportunity are 0.240 for adults and 0.134 for yearlings. Migratory survival decreases and the oversummering rate increases with migration distance, as assessed by culmen length. Conclusions: Our results support the life history hypothesis that oversummering raises survival enough to compensate for the loss of a breeding opportunity. Greater migration distance lowers survival and increases the probability of oversummering. DOI PubMed
168. Bos, D; Kentie, R; La Haye, M; Ydenberg, RC. (2019) Evidence for the effectiveness of controlling muskrat (Ondatra zibethicus L.) populations by trapping.Eur. J. Wildl. Res. 65 Evidence for the effectiveness of controlling muskrat (Ondatra zibethicus L.) populations by trapping
Capture-mark-recapture; Invasive alien species (IAS); Pest species; Population dynamics; Trapping
Unambiguous evidence for the effectiveness of muskrat (Ondatra zibethicus L.) control in well-established populations in mainland Europe is lacking. Yet, this evidence is important given ongoing public challenges to the need for muskrat control and the expressed political aim of the European Union to eradicate invasive alien species, including the muskrat. In this study, indices of muskrat abundance based on livetrapping were compared among (i) sites at which muskrat control had been suspended for 3years (suspended trapping), (ii) sites with ongoing control by kill trapping (ongoing trapping) and (iii) a site at which control efforts had ceased more than 8years previously (no trapping). In the no trapping site, the muskrat abundance index was variable but consistently high, while in the ongoing trapping sites, the muskrat abundance index was consistently low. In the suspended trapping sites, the index of muskrat abundance increased from a level near that of the ongoing trapping sites to that of the no trapping sites. The findings are corroborated by population estimates based on data from robust design mark-recapture models and data from kill trapping. The results are interpreted as compelling proof for an effect of control on muskrat numbers, a basic premise of the control programme. DOI
167. Ellison, AM; Ydenberg, R. (2019) Risk allocation: acute and chronic predator exposure have contrasting effects on Song Sparrow (Melospiza melodia) singing behaviour.Can. J. Zool. 97 Risk allocation: acute and chronic predator exposure have contrasting effects on Song Sparrow (Melospiza melodia) singing behaviour
risk allocation; predation danger; singing behaviour; songbirds; raptors
Increasing the danger posed by predators may cause prey animals to alter their behaviour. For example, they may be more vigilant and so feed more slowly. Breeding male Song Sparrows (Melospiza melodia (A. Wilson, 1810)) spend much time in conspicuous, loud song, which is an important behaviour for territorial defense and for mate attraction. We measured their singing behaviour in relation to both chronic (active Cooper's Hawk (Accipiter cooperii (Bonaparte, 1828)) nest nearby) and acute (playback of hawk calls) predator exposure. We found that proximity to a Cooper's Hawk nest had little or no influence. In contrast, the response to acute exposure was strong and immediate: Song Sparrows reduced the song rate and the proportion of time spent singing, lowered perch height, and increased concealment. The decline in the amount of song during the few minutes following playback attributable to the acute exposure was 34.6%. We analyze these results in light of theories about how animals adjust risk taking in response to predation danger. Given that the numbers of their predators have risen steadily for the past few decades and affect the level of singing, we consider the implications for trend estimates of songbird populations based on surveys using auditory methods. DOI
166. Grishchenko, M; Prins, HHT; Ydenberg, RC; Schaepman, ME; de Boer, WF; de Knegt, HJ. (2019) Land use change and the migration geography of Greater White-fronted geese in European Russia.Ecosphere 10 Land use change and the migration geography of Greater White-fronted geese in European Russia
agriculture; geese migration; land use change; political ecology; Russia; stopover sites
Large areas of agricultural land have been abandoned in European Russia since 1991, triggering succession toward more wooded landscapes, especially in northern regions where conditions for agriculture are more challenging. We hypothesize that this process has contributed to a southward shift by migratory Atlantic Greater White-fronted geese, as stopover sites in northern Russia became progressively less suitable. To test this hypothesis, we located stopover sites from information contained in 2976 ring recoveries and sightings of neck-collared geese. These records were divided into three time periods, chosen to reflect major changes in the economy and land use of European Russia: 1960-1990, 1991-2000, and 2001-2013. We used a kernel density estimator grid to delineate areas surrounding 300 putative stopover sites, and statistically evaluated the effects of latitude, distance to nearest waterbody, settlement, and period on stopover site usage by geese. Our results show that over the three periods, usage of the stopover sites has shifted southward, indicating that Greater White-fronted geese have shifted their migration pathway, with the greatest shift in the most recent period. This shift was confirmed by a highly significant squared latitude term and significant interaction term between periods. The nearest settlements showed no significant effect on stopover site usage while the nearest waterbody term was negative, suggesting higher waterbody densities contributed to higher densities of stopover sites. We attribute the shift to the successional reforestation of the Russian landscape that has followed widespread land abandonment, especially that following the break-up of the former USSR. DOI
164.Ydenberg, RC; Hope, DD. (2019) Danger management and the seasonal adjustment of migratory speed by sandpipers.J. Avian Biol. 50 Danger management and the seasonal adjustment of migratory speed by sandpipers
danger minimizing; migration; migration speed
The behavior of migrating birds is governed by time-, energy- and danger-minimizing strategies. The adjustment of migration speed (i.e. the rate at which distance is covered during a migration) is a behavioral tactic that might contribute to these strategic goals. Shorter stopovers and greater fuel loads increase migration speed, but both require more intensive foraging at stopovers, making migrants more vulnerable to predators. A simple numerical model shows how seasonal alterations in migration speed can lower the exposure of western sandpipers to peregrine falcons, their most important predator. The 'caution-speed-caution' pattern of higher migration speed in the mid-passage period, observed in earlier work, requires that the intensive foraging necessary heightens vulnerability, and that migrants are exposed to both migrant predators as well as predators resident at migratory stopovers. DOI
163. van den Top, GG; Reynolds, JD; Prins, HHT; Mattsson, J; Green, DJ; Ydenberg, RC. (2018) From salmon to salmonberry: The effects of salmon-derived nutrients on the stomatal density of leaves of the nitriphilic shrub Rubus spectabilis.Funct. Ecol. 32 From salmon to salmonberry: The effects of salmon-derived nutrients on the stomatal density of leaves of the nitriphilic shrub Rubus spectabilis
Great Bear Rainforest; nutrient subsidy; Rubus spectabilis; salmonberry; salmon-derived nutrients; stomata; stomatal density
Nutrients derived from the carcasses of Pacific salmon have been shown to have wide-ranging effects on riparian systems. These include changes in community species composition and an increase in leaf nitrogen concentration, with the latter effect pronounced in the nitriphilic shrub Rubus spectabilis (salmonberry). Experimental work with other species has shown that leaf stomatal density increases in response to nitrogen fertilization. We predicted that the stomatal density of salmonberry leaves would vary directly with the density of spawning salmon in salmonberry leaves collected from 16 streams in the vicinity of Bella Bella, on British Columbia's central coast. We estimated the stomatal density along each stream, and quantified stream characteristics, including the number of spawning salmon (Oncorhynchus spp.), canopy cover, stem density and soil moisture. We found that salmon have both direct and indirect effects on stomatal density, the latter mediated by canopy cover and stem density. Salmonberry stomatal density increased by 1.12 stomata per mm(2) (similar to 0.5%) for every kg of salmon per metre of stream. Over the range of salmon densities observed (1.8-49.0 kg per metre of stream), stomatal density increased by almost 45 mm(-2), or more than 20%. These data confirm that the stomatal density in salmonberry responds positively to the opportunity for greater productivity provided by salmon carcasses. The data provide insight into the physiological and morphological processes supporting nitrogen uptake, which in turn influences plant community composition. A is available for this article. DOI
162. Dehn, MM; Ydenberg, RC; Dill, LM. (2017) Experimental addition of cover lowers the perception of danger and increases reproduction in meadow voles (Microtus pennsylvanicus).Can. J. Zool. 95: 463-472 Experimental addition of cover lowers the perception of danger and increases reproduction in meadow voles (Microtus pennsylvanicus)
meadow voles; Microtus pennsylvanicus; reproduction; predation danger; field experiment; cover; giving up density; activity; individual decisions; life history
Predation danger is pervasive for small mammals and is expected to select strongly for behavioural tactics that reduce the risk. In particular, since it may be considered a cost of reproduction, predation danger is expected to affect the level of reproductive effort. We test this hypothesis in a population of meadow voles (Microtus pennsylvanicus (Ord, 1815)) under seminatural conditions in field enclosures. We manipulated the voles' perception of predation danger by adjusting the available cover and measured giving up density (GUD) in food patches to verify that the perception of danger differed between high-and low-cover treatments. Treatments did not differ in actual predation rate, in vole density, or in the quantity or quality of food. During the experiments, we measured indices of vole reproductive effort including activity (electronic detectors), foraging intensity (fecal plates), and the number of young produced (livetrapping). Voles in the high-cover (lower danger) treatments were more active, foraged more, and produced 85% more young per female per trap period than voles in the low-cover (higher danger) treatment. We briefly discuss the population consequences of this adaptive behavioural flexibility. DOI
161. Katinic, PJ; Patterson, DA; Ydenberg, RC. (2017) Condition dependence in the marine exit timing of sockeye salmon (Oncorhynchus nerka) returning to Copper Creek, Haida Gwaii.Canadian Journal of Fisheries and Aquatic Sciences 74: 15-22 Condition dependence in the marine exit timing of sockeye salmon (Oncorhynchus nerka) returning to Copper Creek, Haida Gwaii
We examined a small population of sockeye salmon (Oncorhynchus nerka) that enters their natal stream, to hold in their natal lake, months (>130 days) prior to spawning. This effectively decouples the influence of spawn timing requirements and behaviours from river entry (alternately referred to as "marine exit") timing and is therefore a good model to study the migration strategies specifically associated with marine exit. We found individuals with early marine exit had higher growth rates in the months prior to river entry, had greater lipid density, were more likely male, more likely of the 2.2 versus 1.2 age class, had smaller gonads, and (if female) had more and smaller eggs. Body size at river entry did not vary seasonally. These patterns are explained using a life history model proposing that individual fish exit the sea when the marginal fitness benefits of further growth are outweighed by the marginal fitness cost of further marine residence. This point is reached at different times depending on body size, sex, lipid reserves, and the growth rate. DOI
160. Lank, DB; Xu, CL; Harrington, BA; Morrison, RIG; Gratto-Trevor, CL; Hicklin, PW; Sandercock, BK; Smith, PA; Kwon, E; Rausch, J; Dominix, LDP; Hamilton, DJ; Paquet, J; Bliss, SE; Neima, SG; Friis, C; Flemming, SA; Anderson, AM; Ydenberg, RC. (2017) Long-term continental changes in wing length, but not bill length, of a long-distance migratory shorebird.Ecol. Evol. 7: 3243-3256 Long-term continental changes in wing length, but not bill length, of a long-distance migratory shorebird
allometry; Calidris pusilla; environmental change; phenotypical change; predation risk; semipalmated sandpiper
We compiled a > 50-year record of morphometrics for semipalmated sandpipers (Calidris pusilla), a shorebird species with a Nearctic breeding distribution and intercontinental migration to South America. Our data included > 57,000 individuals captured 1972-2015 at five breeding locations and three major stopover sites, plus 139 museum specimens collected in earlier decades. Wing length increased by ca. 1.5 mm (> 1%) prior to 1980, followed by a decrease of 3.85 mm (nearly 4%) over the subsequent 35 years. This can account for previously reported changes in metrics at a migratory stopover site from 1985 to 2006. Wing length decreased at a rate of 1,098 darwins, or 0.176 haldanes, within the ranges of other field studies of phenotypic change. Bill length, in contrast, showed no consistent change over the full period of our study. Decreased body size as a universal response of animal populations to climate warming, and several other potential mechanisms, are unable to account for the increasing and decreasing wing length pattern observed. We propose that the post-WWII near-extirpation of falcon populations and their post-1973 recovery driven by the widespread use and subsequent limitation on DDT in North America selected initially for greater flight efficiency and latterly for greater agility. This predation danger hypothesis accounts for many features of the morphometric data and deserves further investigation in this and other species. DOI
159. Ottenburghs, J; Kraus, RHS; van Hooft, P; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2017) Avian introgression in the genomic era.Avian Res. 8 Avian introgression in the genomic era
Admixture; Cline theory; D-statictic; Genomic landscape; Hybridization; Phylogenetic discordance
Introgression, the incorporation of genetic material from one (sub) species into the gene pool of another by means of hybridization and backcrossing, is a common phenomenon in birds and can provide important insights into the speciation process. In the last decade, the toolkit for studying introgression has expanded together with the development of molecular markers. In this review, we explore how genomic data, the most recent step in this methodological progress, impacts different aspects in the study of avian introgression. First, the detection of hybrids and backcrosses has improved dramatically. The most widely used software package is STRUCTURE. Phylogenetic discordance (i.e. different loci resulting in discordant gene trees) is another means for the detection of introgression, although it should be regarded as a starting point for further analyses, not as a definitive proof of introgression. Specifically, disentangling introgression from other biological processes, such as incomplete lineage sorting, remains a challenging endeavour, although new techniques, such as the D-statistic, are being developed. In addition, phylogenetics might require a shift from trees to networks. Second, the study of hybrid zones by means of geographical or genomic cline analysis has led to important insights into the complex interplay between hybridization and speciation. However, because each hybrid zone study is just a single snapshot of a complex and continuously changing interaction, hybrid zones should be studied across different temporal and/or spatial scales. A third powerful tool is the genome scan. The debate on which evolutionary processes underlie the genomic landscape is still ongoing, as is the question whether loci involved in reproductive isolation cluster together in 'islands of speciation' or whether they are scattered throughout the genome. Exploring genomic landscapes across the avian tree of life will be an exciting field for further research. Finally, the findings from these different methods should be incorporated into specific speciation scenarios, which can consequently be tested using a modelling approach. All in all, this genomic perspective on avian hybridization and speciation will further our understanding in evolution in general. DOI
158. Ottenburghs, J; Megens, HJ; Kraus, RHS; van Hooft, P; van Wieren, SE; Crooijmans, RPMA; Ydenberg, RC; Groenen, MAM; Prins, HHT. (2017) A history of hybrids? Genomic patterns of introgression in the True Geese.BMC Evol. Biol. 17 A history of hybrids? Genomic patterns of introgression in the True Geese
Hybridization; Phylogenetic Networks; D-statistic; PSMC; Phylogenomics
Background: The impacts of hybridization on the process of speciation are manifold, leading to distinct patterns across the genome. Genetic differentiation accumulates in certain genomic regions, while divergence is hampered in other regions by homogenizing gene flow, resulting in a heterogeneous genomic landscape. A consequence of this heterogeneity is that genomes are mosaics of different gene histories that can be compared to unravel complex speciation and hybridization events. However, incomplete lineage sorting (often the outcome of rapid speciation) can result in similar patterns. New statistical techniques, such as the D-statistic and hybridization networks, can be applied to disentangle the contributions of hybridization and incomplete lineage sorting. We unravel patterns of hybridization and incomplete lineage sorting during and after the diversification of the True Geese (family Anatidae, tribe Anserini, genera Anser and Branta) using an exon-based hybridization network approach and taking advantage of discordant gene tree histories by re-sequencing all taxa of this clade. In addition, we determine the timing of introgression and reconstruct historical effective population sizes for all goose species to infer which demographic or biogeographic factors might explain the observed patterns of introgression. Results: We find indications for ancient interspecific gene flow during the diversification of the True Geese and were able to pinpoint several putative hybridization events. Specifically, in the genus Branta, both the ancestor of the White-cheeked Geese (Hawaiian Goose, Canada Goose, Cackling Goose and Barnacle Goose) and the ancestor of the Brent Goose hybridized with Red-breasted Goose. One hybridization network suggests a hybrid origin for the Red-breasted Goose, but this scenario seems unlikely and it not supported by the D-statistic analysis. The complex, highly reticulated evolutionary history of the genus Anser hampered the estimation of ancient hybridization events by means of hybridization networks. The reconstruction of historical effective population sizes shows that most species showed a steady increase during the Pliocene and Pleistocene. These large effective population sizes might have facilitated contact between diverging goose species, resulting in the establishment of hybrid zones and consequent gene flow. Conclusions: Our analyses suggest that the evolutionary history of the True Geese is influenced by introgressive hybridization. The approach that we have used, based on genome-wide phylogenetic incongruence and network analyses, will be a useful procedure to reconstruct the complex evolutionary histories of many naturally hybridizing species groups. DOI
157. van Loon, EE; Bos, D; Hubard, CJV; Ydenberg, RC. (2017) A historical perspective on the effects of trapping and controlling the muskrat (Ondatra zibethicus) in the Netherlands.Pest Management Science 73: 305-312 A historical perspective on the effects of trapping and controlling the muskrat (Ondatra zibethicus) in the Netherlands
historical data; muskrat; pest species; population dynamics; trapping intensity
BACKGROUND: The muskrat is considered to be a pest species in the Netherlands, and a year-round control programme is in effect. We aimed to evaluate the effectiveness of this programme using historical data on catch and effort collected at a provincial scale. RESULTS: The development of the catch differed between provinces, depending on the year of colonisation by muskrat and the investment of effort ( measured as field hours). The catch did not peak in the same year for the various provinces, and provinces that were colonised earlier in time took longer to attain the peak catch. Trapping resulted in declining populations, but only after a certain threshold of annual effort in trapping had been surpassed. On average, populations were observed to decline when the annual effort exceeded 1.4 field hours per km of waterway for several successive years. Having reached a phase of greater control, control organisations tended to reduce effort. CONCLUSION: We conclude that control measures can make muskrat populations decline, provided that the effort is commensurate with the population size. Our study emphasises that experimentation is needed to confirm the causality of the findings, to establish the relation with damage or safety risk and to derive an optimal control strategy. (C) 2016 Society of Chemical Industry DOI
156. Willie, M; Esler, D; Boyd, WS; Molloy, P; Ydenberg, RC. (2017) Spatial variation in polycyclic aromatic hydrocarbon exposure in Barrow's goldeneye (Bucephala islandica) in coastal British Columbia.Mar. Pollut. Bull. 118: 167-179 Spatial variation in polycyclic aromatic hydrocarbon exposure in Barrow's goldeneye (Bucephala islandica) in coastal British Columbia
British Columbia; Bucephala islandica; CYP1A; Hydrocarbon; Biomarker; Mussel
Barrow's goldeneyes are sea ducks that winter throughout coastal British Columbia (BC). Their diet consists primarily of intertidal blue mussels, which can accumulate PAHs; accordingly, goldeneyes may be susceptible to exposure through contaminated prey. In 2014/15, we examined total PAH concentrations in mussels from undeveloped and developed coastal areas of BC At those same sites, we used EROD to measure hepatic CYP1A induction in goldeneyes. We found higher mussel PAH concentrations at developed coastal sites. Regionally, goldeneyes from southern BC, which has relatively higher coastal development, had higher EROD activity compared to birds from northern BC Our results suggest goldeneyes wintering in coastal BC were exposed to PAHs through diet, with higher exposure among birds wintering in coastal areas with greater anthropogenic influence. These results suggest the mussel-goldeneye system is suitable as a natural, multi-trophic-level indicator of contemporary hydrocarbon contamination, occurrence and exposure useful for establishing oil spill recovery endpoints. (C) 2017 Elsevier Ltd. All rights reserved. DOI
155.Ydenberg, RC; Barrett, J; Lank, DB; Xu, CL; Faber, M. (2017) The redistribution of non-breeding dunlins in response to the post-DDT recovery of falcons.Oecologia 183: 1101-1110 The redistribution of non-breeding dunlins in response to the post-DDT recovery of falcons
Raptor population increases; Non-breeding; biology; Effects of top predators; Shorebirds; Predator-prey distributions
Large-scale changes in predator populations are occurring worldwide due to (re-)introductions, over-exploitation, or recovery after decimation by pesticides and persecution. These widespread changes may affect the distribution of their prey. We studied the continental-scale distributions of non-breeding Calidris alpina pacifica and C. a. hudsonia (Pacific and Atlantic dunlins, respectively), as numbers of their major predators-peregrines (Falco peregrinus) and merlins (F. columbarius; together 'falcons')-increased after DDT was banned in 1973. For the period 1975-2010 we compiled the number of dunlins and falcons in each of 244 Christmas Bird Count circles, which cover most of the dunlins' non-breeding ranges. Over the study period, falcons increased by 6.5- (Pacific) and 3.1- (Atlantic) fold, spread to more count circles, and the number of dunlins per falcon fell. The annual total count of the two dunlin sub-species fluctuated strongly and independently. We measured annual aggregation as the expected proportion of a subspecies total found on the same count circle as a randomly selected dunlin. The average aggregation of Pacific dunlins (0.117) was about double that of Atlantic dunlins (0.059), with annual variation largely attributable to changes in a few large count circles. The slope of the aggregative response to year-on-year changes in dunlin numbers was identical on the two coasts. The response to the ongoing falcon increase was positive and significant on the Pacific and slightly negative on the Atlantic. We interpret these results using a version of the ideal free distribution that includes predation danger. DOI
154. Lukeman, R; Christie, A; Ydenberg, RC. (2016) Goal-dependent current compensation and drift in surf scoter flocks.Mov. Ecol. 4 Goal-dependent current compensation and drift in surf scoter flocks
Current compensation; Drift; Flocking; Collective motion
Background: Animals moving through air or water toward a goal frequently must contend with fluid currents, which can drift the actual path of the animal away from the direction of heading. Whether, and to what degree, animals compensate for currents depends on the species and environmental context, but plays an important role in the movement ecology of the species. In this paper, flocks of surf scoters (Melanitta perspicillata), an aquatic diving duck, were individually tracked during collective foraging in the presence of sideward water currents to assess the individual compensatory response while moving from open water toward the foraging location versus return to open water. Results: During short-range movement toward the foraging location, surf scoters moved more slowly, and compensated for currents by orienting diagonally into the current to maintain a perpendicular track to the goal. In contrast, during return to open water, surf scoters moved faster, and maintained a perpendicular orientation away from the foraging location, and allowed the sideward current to drift their track diagonally. Conclusions: Surf scoters show a behavioural flexibility in response to currents, alternately using compensation and drift as the movement goal and consequent cost of accuracy change. DOI PubMed
153. Ottenburghs, J; Megens, HJ; Kraus, RHS; Madsen, O; van Hooft, P; van Wieren, SE; Crooijmans, RPMA; Ydenberg, RC; Groenen, MAM; Prins, HHT. (2016) A tree of geese: A phylogenomic perspective on the evolutionary history of True Geese.Molecular Phylogenetics and Evolution 101: 303-313 A tree of geese: A phylogenomic perspective on the evolutionary history of True Geese
Consensus; Concatenation; Gene tree; Hybridization; Incomplete lineage sorting; Species tree
Phylogenetic incongruence can be caused by analytical shortcomings or can be the result of biological processes, such as hybridization, incomplete lineage sorting and gene duplication. Differentiation between these causes of incongruence is essential to unravel complex speciation and diversification events. The phylogeny of the True Geese (tribe Anserini, Anatidae, Anseriformes) was, until now, contentious, i.e., the phylogenetic relationships and the timing of divergence between the different goose species could not be fully resolved. We sequenced nineteen goose genomes (representing seventeen species of which three subspecies of the Brent Goose, Branta bernicla) and used an exon-based phylogenomic approach (41,736 exons, representing 5887 genes) to unravel the evolutionary history of this bird group. We thereby provide general guidance on the combination of whole genome evolutionary analyses and analytical tools for such cases where previous attempts to resolve the phylogenetic history of several taxa could not be unravelled. Identical topologies were obtained using either a concatenation (based upon an alignment of 6,630,626 base pairs) or a coalescent-based consensus method. Two major lineages, corresponding to the genera Anser and Branta, were strongly supported. Within the Branta lineage, the Whitecheeked Geese form a well-supported sub-lineage that is sister to the Red-breasted Goose (Branta ruficollis). In addition, two main clades of Anser species could be identified, the White Geese and the Grey Geese. The results from the consensus method suggest that the diversification of the genus Anser is heavily influenced by rapid speciation and by hybridization, which may explain the failure of previous studies to resolve the phylogenetic relationships within this genus. The majority of speciation events took place in the late Pliocene and early Pleistocene (between 4 and 2 million years ago), conceivably driven by a global cooling trend that led to the establishment of a circumpolar tundra belt and the emergence of temperate grasslands. Our approach will be a fruitful strategy for resolving many other complex evolutionary histories at the level of genera, species, and subspecies. (C) 2016 Elsevier Inc. All rights reserved. DOI
152. Ottenburghs, J; van Hooft, P; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2016) Birds in a bush: Toward an avian phylogenetic network.Auk 133: 577-582 Birds in a bush: Toward an avian phylogenetic network
phylogenetics; hybridization; phylogenetic networks; adaptive radiation; genomics
Reconstructing the avian tree of life has become one of the major goals in ornithology. The use of genomic tools seemed a promising approach to reach this goal, but, instead, phylogenetic analyses of large numbers of genes uncovered high levels of incongruence between the resulting gene trees. This incongruence can be caused by several biological processes, such as recombination, hybridization, and rapid speciation (which can lead to incomplete lineage sorting). These processes directly or indirectly amount to deviations from tree-like patterns, thereby thwarting the use of phylogenetic trees. Phylogenetic networks provide an ideal tool to deal with these difficulties. We illustrate the usefulness of phylogenetic networks to capture the complexity and subtleties of diversification processes by discussing several recent genomic analyses of birds in general and the well-known radiation of Darwin's finches. With the increasing amount of genomic data in avian phylogenetic studies, capturing the evolutionary history of a set of taxa in a phylogenetic tree will become increasingly difficult. Moreover, given the widespread occurrence of hybridization and the numerous adaptive radiations in birds, phylogenetic networks provide a powerful tool to display and analyse the evolutionary history of many bird groups. The genomic era might thus result in a paradigm shift in avian phylogenetics from trees to bushes. DOI
151. Ottenburghs, J; van Hooft, P; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2016) Hybridization in geese: a review.Frontiers in Zoology 13 Hybridization in geese: a review
Hybridization; Introgression; Behaviour; Nest parasitism; Extra-pair copulations; Fertility; Anatidae; Captivity
The high incidence of hybridization in waterfowl (ducks, geese and swans) makes this bird group an excellent study system to answer questions related to the evolution and maintenance of species boundaries. However, knowledge on waterfowl hybridization is biased towards ducks, with a large knowledge gap in geese. In this review, we assemble the available information on hybrid geese by focusing on three main themes: (1) incidence and frequency, (2) behavioural mechanisms leading to hybridization, and (3) hybrid fertility. Hybridization in geese is common on a species-level, but rare on a per-individual level. An overview of the different behavioural mechanisms indicates that forced extra-pair copulations and interspecific nest parasisitm can both lead to hybridization. Other sources of hybrids include hybridization in captivity and vagrant geese, which may both lead to a scarcity of conspecifics. The different mechanisms are not mutually exclusive and it is currently not possible to discriminate between the different mechanisms without quantitative data. Most hybrid geese are fertile; only in crosses between distantly related species do female hybrids become sterile. This fertility pattern, which is in line with Haldane's Rule, may facilitate interspecific gene flow between closely related species. The knowledge on hybrid geese should be used, in combination with the information available on hybridization in ducks, to study the process of avian speciation. DOI
150. Reurink, F; Hentze, N; Rourke, J; Ydenberg, R. (2016) Site-specific flight speeds of nonbreeding Pacific dunlins as a measure of the quality of a foraging habitat.Behavioral Ecology 27: 803-809 Site-specific flight speeds of nonbreeding Pacific dunlins as a measure of the quality of a foraging habitat
dunlin; foraging theory; optimal flight speed; shorebird habitat quality
Many studies have investigated how foraging behavior such as prey choice varies with factors such as prey size or density. Models of such relationships can be applied "in reverse" to translate easily observed foraging behaviors into assays of habitat attributes that cannot (easily) be measured directly. One such model analyzes the speed of a forager flying between patches, where it captures prey. Faster flight shortens the travel time and hence elevates the intake rate, but is increasingly expensive. The model shows that the net intake rate is maximized at the point at which the energetic cost of flight is equivalent to the net rate of intake. Easy-to-measure flight speeds can thus be translated into hard-to-measure foraging intake rates using established flight power relationships. We studied nonbreeding Pacific dunlins (Calidris alpina pacifica) at 4 intertidal sites on the Fraser River estuary, British Columbia, Canada. These sites differed sufficiently that we expected food availability and hence the attainable foraging rate to differ. We measured interpatch flight speeds of dunlins foraging along the tideline within each site. The measured ground speed, calculated airspeed, and the statistically derived zero-wind effect airspeed all differed significantly between sites, matching in rank order our expectation of habitat quality based on their physical differences. Intake rate estimates ranged from 4.10 W (best mudflat) to 3.48 W (poorest). We think it unlikely that we would have been able to find such small differences using direct measures of foraging intake. DOI
149.Ydenberg, RC; Hemerik, L. (2016) Division of labour by provisioners.Evol. Ecol. Res. 17: 671-683 Division of labour by provisioners
central place foraging; collection of fuel vs. cargo resources; division of labour; provisioning; social evolution; teamwork
Question: Animals of many species work as members of a group such as a pair or colony to provision various resources to a central place. Group members could work as generalists (all group members self-feed to obtain fuel and deliver cargo; e.g. food items for offspring, non-food items such as building materials) or as specialists (collect only fuel, or only cargo). Mathematical method: We developed a simple analytical model to investigate conditions favouring these basic alternatives. Key assumptions: We assumed that natural selection favours mechanisms that maximize the delivery rate of cargo, fuel being important only in so far as it enables the work of the delivery of cargo to be supported. Conclusions: The model shows that this division of labour boosts the aggregate rate of cargo delivery when the round trip time a provisioner saves by not having to forage for its own fuel more than offsets the required allocation of group members to exclusive fuel collection. We note that groups with this provisioning division of labour are common in social insects, but appear absent among vertebrates. Several hypotheses may explain this marked difference. We suggest that provisioning by division of labour represents an early step in social evolution that was greatly elaborated in the bees and ants.
148. Goedbloed, DJ; van Hooft, P; Lutz, W; Megens, HJ; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2015) Increased Mycoplasma hyopneumoniae Disease Prevalence in Domestic Hybrids Among Free-Living Wild Boar.EcoHealth 12: 571-579 Increased Mycoplasma hyopneumoniae Disease Prevalence in Domestic Hybrids Among Free-Living Wild Boar
hybrid; porcine enzootic pneumonia; Sus scrofa; wildlife disease; wildlife-domestic interface; introgression; deleterious alleles
Wildlife immune genes are subject to natural selection exerted by pathogens. In contrast, domestic immune genes are largely protected from pathogen selection by veterinary care. Introgression of domestic alleles into the wild could lead to increased disease susceptibility, but observations are scarce due to low introgression rates, low disease prevalence and reduced survival of domestic hybrids. Here we report the first observation of a deleterious effect of domestic introgression on disease prevalence in a free-living large mammal. A fraction of 462 randomly sampled free-living European wild boar (Sus scrofa) was genetically identified as recent wild boar-domestic pig hybrids based on 351 SNP data. Analysis of antibody prevalence against the bacterial pathogen Mycoplasma hyopneumoniae (Mhyo) showed an increased Mhyo prevalence in wild-domestic hybrids. We argue that the most likely mechanism explaining the observed association between domestic hybrid status and Mhyo antibody prevalence would be introgression of deleterious domestic alleles. We hypothesise that large-scale use of antibiotics in the swine breeding sector may have played a role in shaping the relatively deleterious properties of domestic swine immune genes and that domestic introgression may also lead to increased wildlife disease susceptibility in the case of other species. DOI PubMed
147. Jimenez, A; Elner, RW; Favaro, C; Rickards, K; Ydenberg, RC. (2015) Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration.Estuarine Coastal and Shelf Science 155: 8-16 Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration
aquatic birds; biofilm; feeding; food availability; tidal flats
The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpine) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration. (C) 2015 Elsevier Ltd. All rights reserved. DOI
146. Katinic, PJ; Patterson, DA; Ydenberg, RC. (2015) Thermal regime, predation danger and the early marine exit of sockeye salmon Oncorhynchus nerka.Journal of Fish Biology 86: 276-287 Thermal regime, predation danger and the early marine exit of sockeye salmon Oncorhynchus nerka
Copper Creek; Haida Gwaii; life-history strategy; river entry; timing of migration
Marine exit timing of sockeye salmon Oncorhynchus nerka populations on the Haida Gwaii Archipelago, British Columbia, Canada, is described, with specific focus on Copper Creek. Marine exit in Copper Creek occurs>130days prior to spawning, one of the longest adult freshwater residence periods recorded for any O. nerka population. Copper Creek presents an easy upstream migration, with mild water temperatures (7 to 14 degrees C), short distance (131km) and low elevation gain (41m) to the lake where fish hold prior to spawning. An energetic model estimates that <1% of the initial energy reserve is required for upstream migration, compared with 62% for lake holding and 38% for reproductive development. Historical records suggest that it is unlikely that water temperature in any of the O.nerka streams in Haida Gwaii has ever exceeded the presumed temperature threshold (19 degrees C) for early marine exit. Although it is not impossible that the thermal tolerance of Copper Creek O.nerka is very low, the data presented here appear inconsistent with thermal avoidance as an explanation for the early marine exit timing in Copper Creek and in three other populations on the archipelago with early marine exit. DOI PubMed
144. Si, YL; Xin, QC; de Boer, WF; Gong, P; Ydenberg, RC; Prins, HHT. (2015) Do Arctic breeding geese track or overtake a green wave during spring migration?Scientific Reports 5 Do Arctic breeding geese track or overtake a green wave during spring migration?
Geese breeding in the Arctic have to do so in a short time-window while having sufficient body reserves. Hence, arrival time and body condition upon arrival largely influence breeding success. The green wave hypothesis posits that geese track a successively delayed spring flush of plant development on the way to their breeding sites. The green wave has been interpreted as representing either the onset of spring or the peak in nutrient biomass. However, geese tend to adopt a partial capital breeding strategy and might overtake the green wave to accomplish a timely arrival on the breeding site. To test the green wave hypothesis, we link the satellite-derived onset of spring and peak in nutrient biomass with the stopover schedule of individual Barnacle Geese. We find that geese track neither the onset of spring nor the peak in nutrient biomass. Rather, they arrive at the southernmost stopover site around the peak in nutrient biomass, and gradually overtake the green wave to match their arrival at the breeding site with the local onset of spring, thereby ensuring gosling benefit from the peak in nutrient biomass. Our approach for estimating plant development stages is critical in testing the migration strategies of migratory herbivores. DOI PubMed
143. St Clair, CT; Baird, P; Ydenberg, R; Elner, R; Bendell, LI. (2015) Trace elements in pacific Dunlin (Calidris alpina pacifica): patterns of accumulation and concentrations in kidneys and feathers.Ecotoxicology 24: 29-44 Trace elements in pacific Dunlin (Calidris alpina pacifica): patterns of accumulation and concentrations in kidneys and feathers
Cadmium; Dunlin; Habitat preference; Risk assessment; Selenium; Trace elements
Trace element concentrations were measured in Pacific Dunlin (Calidris alpina pacifica) to identify factors that influence accumulation and to assess toxicity risks. We report concentrations of cadmium, copper, and zinc in kidneys as well as copper, lead, mercury, selenium and zinc in feathers. Relationships between element concentrations and Dunlin age, sex, bill length, habitat preference, trophic level, and sample group were investigated with regression analyses. Stable isotope ratios of carbon and nitrogen in Dunlin muscle tissue were used to determine habitat preference and trophic level, respectively. Cadmium concentrations in kidneys were significantly related to habitat preference: [Cd] in estuarine foragers >[Cd] in terrestrial foragers. Cadmium accumulation was age-dependent as concentrations increased significantly within 10 months of hatch dates but not afterward. Concentrations of cadmium and zinc in kidneys as well as lead and mercury in feathers were below those known to cause deleterious effects in birds. In contrast, selenium concentrations in feathers (range: 2.1-14.0 A mu g/g) were often at levels associated with toxicity risks (> 5 A mu g/g). Toxicity thresholds are not available for copper in kidneys or copper and zinc in feathers; however, measured concentrations of these elements were within documented ranges for sandpipers. Future studies should assess potential impacts of selenium on embryonic development in Dunlin and other sandpipers. Risk assessments would yield more conclusive results for all elements if impacts under ecologically relevant stresses (e.g. development in the wild, migration, predation) were better understood. DOI PubMed
142. Xu, CL; Barrett, J; Lank, DB; Ydenberg, RC. (2015) Large and irregular population fluctuations in migratory Pacific (Calidris alpina pacifica) and Atlantic (C-a. hudsonica) dunlins are driven by density-dependence and climatic factors.Population Ecology 57: 551-567 Large and irregular population fluctuations in migratory Pacific (Calidris alpina pacifica) and Atlantic (C-a. hudsonica) dunlins are driven by density-dependence and climatic factors
Annual cycle; Christmas bird counts; Large scale analysis; Migratory shorebirds; Population dynamics; Seasonal environmental conditions
Understanding the forces driving population dynamics is critical for species conservation and population management. For migratory birds, factors that regulate population abundance could come from effects experienced on breeding areas, wintering grounds, or during migration. We compiled survey data for Pacific and Atlantic subspecies of dunlins (Calidris alpina pacifica and C. a. hudsonica) from range-wide Christmas bird counts (1975-2010), and investigated the influences on this population index of density-dependence, falcon numbers, a set of seasonal environmental conditions during breeding, migration and non-breeding periods, and large-scale meteorological measures. For both sub-species, numbers fluctuated irregularly, varying threefold over the survey period, with no long-term upward or downward trend. Based on Royama's general model framework, the change in numbers between successive years for both sub-species was negatively affected by the total count in the previous year (i.e., negative density-dependence) and by the eastward component of storm movement during fall migration, with slower motion associated with higher population growth. The remaining environmental factors differed between the sub-species (snowmelt date on the Pacific, temperature on the Atlantic) or acted in opposite directions (soil moisture). The directional effects of each of these factors are consistent with the biology of dunlin, and together they explain 67.4 (72.9 %) of the variation in the rate of change of Pacific (Atlantic) dunlin annual counts. Falcon numbers were not predictive, despite a tenfold increase in abundance, suggesting compensatory mortality. This study highlights directions for future studies, and provides a model for the analysis of other migratory species. DOI
141. Goedbloed, DJ; van Hooft, P; Megens, HJ; Bosch, T; Lutz, W; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2014) Host genetic heterozygosity and age are important determinants of porcine circovirus type 2 disease prevalence in European wild boar.Eur. J. Wildl. Res. 60: 803-810 Host genetic heterozygosity and age are important determinants of porcine circovirus type 2 disease prevalence in European wild boar
Wild boar; Porcine circovirus type 2; Heterozygosity-fitness correlation; Wildlife disease; Disease mortality
Emerging and zoonotic diseases are important challenges for veterinary and public health. It is therefore a key issue to assess the relative importance of various factors for disease dynamics and to understand the mechanisms behind these factors and interactions. Here, we evaluate the influence of a number of demographic and genetic factors on porcine circovirus type 2 (PCV2) antibody prevalence in the European wild boar (Sus scrofa). We measured PCV2 blood serum antibody levels of 462 randomly sampled wild boars from a cross-border area in the Netherlands and western parts of Germany in a 3-year period. These samples were also genotyped using a randomly selected genome-wide 351 SNP assay. Generalized linear mixed model analysis shows that wild boar PCV2 antibody status is determined by age and genetic heterozygosity, with an idiosyncratic influence of the year of sampling. In contrast, sex, population membership and domestic hybrid status did not significantly affect PCV2 antibody status. The observed positive relationship between PCV2 antibody status and age is most likely caused by cumulative exposure and PCV2-typical intracellular hiding behaviour. The observed positive relationship between wild boar genetic heterozygosity and PCV2 antibody status could be attributed to disappearance of relatively inbred (low-heterozygosity) individuals. This finding suggests that PCV2 can act as a selective force in wild boar populations and that disease mortality can be mediated by host heterozygosity. DOI
140. Hope, DD; Lank, DB; Ydenberg, RC. (2014) Mortality-minimizing sandpipers vary stopover behavior dependent on age and geographic proximity to migrating predators.Behavioral Ecology and Sociobiology 68: 827-838 Mortality-minimizing sandpipers vary stopover behavior dependent on age and geographic proximity to migrating predators
Predation danger; Flight initiation distance; Vigilance; Predator model; Western sandpiper; Peregrine falcon
Ecological theory for long-distance avian migration considers time-, energy-, and mortality-minimizing tactics, but predictions about the latter have proven elusive. Migrants must make behavioral decisions that can favor either migratory speed or safety from predators, but often not both. We compare the behavior of adult and juvenile western sandpipers Calidris mauri during the course of their temporally segregated passages at a major stopover site. Here, the passage and winter arrival of an important predator, the peregrine falcon Falco peregrinus begins near the end of the adult sandpiper passage (July) and increases rapidly through the juvenile passage (August). The mortality-minimizing hypothesis predicts that as the falcon front is distant but approaching, sandpipers should initially increase the fuel-loading rate (lowered vigilance and predator apprehension) to increase migration speed and so maintain their head start. As the falcon front gains proximity to and passes over the stopover site, sandpipers should become increasingly cautious. Our measurements show that adults decreased vigilance during the period prior to falcon arrival, and had lower vigilance overall than juveniles. Juveniles were more apprehensive, flying further and longer in response to disturbance by a falcon silhouette. This trend was reversed in response to a human approach. Both groups were more vigilant and more apprehensive in a study year with earlier falcon arrival. These results suggest that late (juvenile) and early (adult) migrants minimize mortality on migration in different ways, adults by increased migratory speed at the expense of caution on stopover sites, and juveniles by increased caution at the expense of speed. DOI
139. Kurvers, RHJM; Straates, K; Ydenberg, RC; van Wieren, SE; Swierstra, PS; Prins, HHT. (2014) Social information use by Barnacle Geese Branta leucopsis, an experiment revisited.Ardea 102: 173-180 Social information use by Barnacle Geese Branta leucopsis, an experiment revisited
Barnacle Geese; foraging; social information use; reproducibility
Reproducing research results is one of the cornerstones of science. However, few biological findings are actually replicated. Here, we repeat a study done more than 35 years ago on social information use in Barnacle Geese. In the original study, models of Barnacle Geese were used to measure how they attracted wild Barnacle Geese (Drent & Swierstra 1977). Models were placed in different locations in a pasture and these models attracted many wild Barnacle Geese, providing strong evidence for the use of social information. 37 years later we repeated this experiment, using the same models, the same area and a similar research protocol. Despite an abundance of wild Barnacle Geese in the area frequently flying over the models, the models did not elicit a landing response. In line with the original study, we scored vigilance rates and abundance of geese. Comparing these data to previous records we found that total abundance increased but that vigilance rates were lower than previously recorded. The decreased vigilance suggests that the landscape has become safer or that competition between geese has intensified; both could explain a reduced use of social information. More generally, our study shows the importance of repeating experiments in ecology, especially in a rapidly changing world. DOI
138. Bustnes, JO; Systad, GH; Ydenberg, RC. (2013) Changing distribution of flocking sea ducks as non-regenerating food resources are depleted.Marine Ecology Progress Series 484: 249-257 Changing distribution of flocking sea ducks as non-regenerating food resources are depleted
EIDERS SOMATERIA-MOLLISSIMA; WINTERING COMMON-EIDERS; EAGLE HALIAEETUS-ALBICILLA; POLYSTICTA-STELLERI; NORTHERN NORWAY; HABITAT SELECTION; MYTILUS-EDULIS; PREY DEPLETION; SURF SCOTERS; SIZE
Sutherland & Anderson (1993; J Theor Biol 160:223-230) considered how the distribution of consumers should change as prey resources fixed at the start of a period of exploitation are depleted by foraging activities. Their model predicts that consumers initially aggregate on a single or a few patches offering the highest feeding rate. As the prey density in those patches is reduced, the feeding rate declines to the level attainable at the next best patches, which are then also exploited. Therefore, an increase in the number of flocks and a decline in flock size should be observed as individuals spread out over the available feeding opportunities. Further, once occupied, a patch is exploited for the remainder of the winter. We tested these predictions with winter survey data on the number, size and location of flocks of common eiders Somateria mollissima and king eiders S. spectabilis wintering in Kvalsundet, a sound in northern Norway. Both species are benthivorous, and there is little or no growth or recruitment of their prey in winter at high-latitude sites. The green sea urchin Strongylocentrotus droebachiensis was the dominant prey of both species in Kvalsundet, and the density of this prey species declined over the winter in kelp beds, the preferred winter habitat of common eiders. Our data showed that both common and king eiders began their winter periods in Kvalsundet aggregated into a few large flocks. As the winter progressed, the distribution changed and birds gathered into more and smaller flocks. In the case of common eiders, flock locations remained fixed once a foraging location began to be exploited. King eiders formed a few large flocks early in the season which drifted in heavy tidal currents, but when these split up into smaller flocks in February, they started to exploit fixed locations. We interpret these results as consistent with the Sutherland & Anderson model. DOI
137. Goedbloed, DJ; Megens, HJ; van Hooft, P; Herrero-Medrano, JM; Lutz, W; Alexandri, P; Crooijmans, RPMA; Groenen, M; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2013) Genome-wide single nucleotide polymorphism analysis reveals recent genetic introgression from domestic pigs into Northwest European wild boar populations.Mol. Ecol. 22: 856-866 Genome-wide single nucleotide polymorphism analysis reveals recent genetic introgression from domestic pigs into Northwest European wild boar populations
domestic pig; hybridization; introgression; single nucleotide polymorphism; Sus scrofa; wild boar
Present-day genetic introgression from domestic pigs into European wild boar has been suggested in various studies. However, no hybrids have been identified beyond doubt mainly because available methods were unable to quantify the extent of introgression and rule out natural processes. Genetic introgression from domestic pigs may have far-reaching ecological consequences by altering traits like the reproduction rate or immunology of wild boar. In this study, we demonstrate a novel approach to investigate genetic introgression in a Northwest (NW) European wild boar data set using a genome-wide single nucleotide polymorphism (SNP) assay developed for domestic pigs. We quantified the extent of introgression using allele frequency spectrum analysis, in silico hybridization simulations and genome distribution patterns of introgressed SNPs. Levels of recent introgression in the study area were expected to be low, as pig farming practices are prevailingly intensive and indoors. However, evidence was found for geographically widespread presence of domestic pig SNPs in 10% of analysed wild boar. This was supported by the identification of two different pig mitochondrial DNA haplotypes in three of the identified hybrid wild boar, suggesting that introgression had occurred from multiple sources (pig breeds). In silico hybridization simulations showed that the level of introgression in the identified hybrid wild boar is equivalent to first-generation hybrids until fifth-generation backcrosses with wild boar. The distribution pattern of introgressed SNPs supported these assignments in four of nine hybrids. The other five hybrids are considered advanced-generation hybrids, resulting from interbreeding among hybrid individuals. Three of nine hybrids were genetically associated with a different wild boar population than the one in which they were sampled. This discrepancy suggests that genetic introgression has occurred through the escape or release of an already hybridized farmed wild boar stock. We conclude that genetic introgression from domestic pigs into NW European wild boar populations is more recent and more common than expected and that genome-wide SNP analysis is a promising tool to quantify recent hybridization in free-living populations. DOI PubMed
136. Goedbloed, DJ; van Hooft, P; Megens, HJ; Langenbeck, K; Lutz, W; Crooijmans, RPMA; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2013) Reintroductions and genetic introgression from domestic pigs have shaped the genetic population structure of Northwest European wild boar.BMC Genet. 14 Reintroductions and genetic introgression from domestic pigs have shaped the genetic population structure of Northwest European wild boar
Background: Population genetic studies focus on natural dispersal and isolation by landscape barriers as the main drivers of genetic population structure. However, anthropogenic factors such as reintroductions, translocations and wild x domestic hybridization may also have strong effects on genetic population structure. In this study we genotyped 351 Single Nucleotide Polymorphism markers evenly spread across the genome in 645 wild boar (Sus scrofa) from Northwest Europe to evaluate determinants of genetic population structure. Results: We show that wild boar genetic population structure is influenced by historical reintroductions and by genetic introgression from domestic pigs. Six genetically distinct and geographically coherent wild boar clusters were identified in the Netherlands and Western Germany. The Dutch Veluwe cluster is known to be reintroduced, and three adjacent Dutch and German clusters are suspected to be a result of reintroduction, based on clustering results, low levels of heterozygosity and relatively high genetic distances to nearby populations. Recent wild x domestic hybrids were found geographically widespread across clusters and at low frequencies (average 3.9%). The relationship between pairwise kinship coefficients and geographic distance showed male-biased dispersal at the population genetic level. Conclusions: Our results demonstrate that wildlife and landscape management by humans are shaping the genetic diversity of an iconic wildlife species. Historical reintroductions, translocation and recent restocking activities with farmed wild boar have all influenced wild boar genetic population structure. The current trend of wild boar population growth and range expansion has recently led to a number of contact zones between clusters, and further admixture between the different wild boar clusters is to be expected. DOI PubMed
135. Jones, IM; Butler, RW; Ydenberg, RC. (2013) Recent switch by the Great Blue Heron Ardea herodias fannini in the Pacific northwest to associative nesting with Bald Eagles (Haliaeetus leucocephalus) to gain predator protection.Canadian Journal of Zoology-Revue Canadienne De Zoologie 91: 489-495 Recent switch by the Great Blue Heron Ardea herodias fannini in the Pacific northwest to associative nesting with Bald Eagles (Haliaeetus leucocephalus) to gain predator protection
COLONIES; ADVANTAGES; HABITAT; MAGPIES
The Great Blue Heron Ardea herodias fannini Chapman, 1901 in the Pacific northwest appears to have modified nesting behaviour in response to the strong recent recovery of the Bald Eagle (Haliaeetus leucocephalus (L., 1766)) population. Previously undescribed, herons now often nest in close association with some breeding eagles, even though eagles depredate heron nestlings, are implicated in the recent reproductive decline of herons, and may induce abandonment of heron breeding colonies. We tested the hypothesis that breeding herons gain protection from the territorial behaviour of eagles. Natural observations and simulated incursions showed that nesting eagles actively repel other eagles within at least 250 m around the nest site, thereby establishing a relatively safe place for herons to nest. Surveys showed that 70% of heron nests and 19% of heron colonies were located within 200 m of eagle nests with high reproductive success. These herons had greater reproductive success than those nesting far from eagle nests. DOI
134. Jonker, RM; Kraus, RHS; Zhang, Q; Van Hooft, P; Larsson, K; Van der Jeugd, HP; Kurvers, RHJM; Van Wieren, SE; Loonen, MJJE; Crooijmans, RPMA; Ydenberg, RC; Groenen, MAM; Prins, HHT. (2013) Genetic consequences of breaking migratory traditions in barnacle geese Branta leucopsis.Mol. Ecol. 22: 5835-5847 Genetic consequences of breaking migratory traditions in barnacle geese Branta leucopsis
admixture; cultural evolution; migration modelling; population genetics; SNP; speciation
Cultural transmission of migratory traditions enables species to deal with their environment based on experiences from earlier generations. Also, it allows a more adequate and rapid response to rapidly changing environments. When individuals break with their migratory traditions, new population structures can emerge that may affect gene flow. Recently, the migratory traditions of the Barnacle Goose Branta leucopsis changed, and new populations differing in migratory distance emerged. Here, we investigate the population genetic structure of the Barnacle Goose to evaluate the consequences of altered migratory traditions. We used a set of 358 single nucleotide polymorphism (SNP) markers to genotype 418 individuals from breeding populations in Greenland, Spitsbergen, Russia, Sweden and the Netherlands, the latter two being newly emerged populations. We used discriminant analysis of principal components, F-ST, linkage disequilibrium and a comparison of geneflow models using migrate-n to show that there is significant population structure, but that relatively many pairs of SNPs are in linkage disequilibrium, suggesting recent admixture between these populations. Despite the assumed traditions of migration within populations, we also show that genetic exchange occurs between all populations. The newly established nonmigratory population in the Netherlands is characterized by high emigration into other populations, which suggests more exploratory behaviour, possibly as a result of shortened parental care. These results suggest that migratory traditions in populations are subject to change in geese and that such changes have population genetic consequences. We argue that the emergence of nonmigration probably resulted from developmental plasticity. DOI PubMed
133. Kraus, RHS; Van Hooft, P; Megens, HJ; Tsvey, A; Fokin, SY; Ydenberg, RC; Prins, HHT. (2013) Global lack of flyway structure in a cosmopolitan bird revealed by a genome wide survey of single nucleotide polymorphisms.Molecular Ecology 22: 41-55 Global lack of flyway structure in a cosmopolitan bird revealed by a genome wide survey of single nucleotide polymorphisms
Anas platyrhynchos; ascertainment bias; coalescent analysis; conservation management; population genomics; single nucleotide polymorphisms
Knowledge about population structure and connectivity of waterfowl species, especially mallards (Anas platyrhynchos), is a priority because of recent outbreaks of avian influenza. Ringing studies that trace large-scale movement patterns have to date been unable to detect clearly delineated mallard populations. We employed 363 single nucleotide polymorphism markers in combination with population genetics and phylogeographical approaches to conduct a population genomic test of panmixia in 801 mallards from 45 locations worldwide. Basic population genetic and phylogenetic methods suggest no or very little population structure on continental scales. Nor could individual-based structuring algorithms discern geographical structuring. Model-based coalescent analyses for testing models of population structure pointed to strong genetic connectivity among the world's mallard population. These diverse approaches all support the conclusion that there is a lack of clear population structure, suggesting that the world's mallards, perhaps with minor exceptions, form a single large, mainly interbreeding population. DOI
132. Dekker, D; Out, M; Tabak, M; Ydenberg, R. (2012) THE EFFECT OF KLEPTOPARASITIC BALD EAGLES AND GYRFALCONS ON THE KILL RATE OF PEREGRINE FALCONS HUNTING DUNLINS WINTERING IN BRITISH COLUMBIA.Condor 114: 290-294 THE EFFECT OF KLEPTOPARASITIC BALD EAGLES AND GYRFALCONS ON THE KILL RATE OF PEREGRINE FALCONS HUNTING DUNLINS WINTERING IN BRITISH COLUMBIA
Bald Eagle; Dunlin; Gyrfalcon; kleptoparasitism; Peregrine Falcon
Kleptoparasitism in birds has been the subject of much research, and the Bald Eagle (Haliaeetus leucocephalus) is a known kleptoparasite. It has been reported to pirate ducks captured by Peregrine Falcons (Falco peregrinus), but ours is the first study to examine the effect of kleptoparasitic Bald Eagles on the kill rate of shorebird-hunting Peregrines and indirectly on a population of Dunlins (Calidris alpina) wintering in coastal British Columbia. Bald Eagles increased seasonally and yearly from October 2008 to January 2011. When eagles were scarce, Peregrines hunted ducks as well as Dunlins. Conversely, when eagles were numerous Peregrines hunted Dunlins only. In 56 instances, one or more eagles closely followed hunting Peregrines and retrieved 13 Dunlins dropped or downed by the falcons. The Peregrines were also kleptoparasitized by Gyrfalcons (Falco rusticolus), which pirated 11 Dunlins from Peregrines. Observed losses to kleptoparasites amounted to 24 (36%) of 67 Peregrines' captures. The kill rate per hour of observation was 0.05 hr(-1) in October and November when eagles and Gyrfalcons were few but significantly higher at 0.18 hr(-1) during January and February. In January 2011, when intraguild kleptoparasites were most abundant, the Peregrine's kill rate was 0.30 hr(-1). These results support the hypothesis that kleptoparasites had an indirect effect on a population of wintering Dunlins because Peregrines compensated for prey lost to kleptoparasites by increasing their kill rate. DOI
131. Franks, SE; Norris, DR; Kyser, TK; Fernandez, G; Schwarz, B; Carmona, R; Colwell, MA; Sandoval, JC; Dondua, A; Gates, HR; Haase, B; Hodkinson, DJ; Jimenez, A; Lanctot, RB; Ortego, B; Sandercock, BK; Sanders, F; Takekawa, JY; Warnock, N; Ydenberg, RC; Lank, DB. (2012) Range-wide patterns of migratory connectivity in the western sandpiper Calidris mauri.Journal of Avian Biology 43: 155-167 Range-wide patterns of migratory connectivity in the western sandpiper Calidris mauri
Understanding the population dynamics of migratory animals and predicting the consequences of environmental change requires knowing how populations are spatially connected between different periods of the annual cycle. We used stable isotopes to examine patterns of migratory connectivity across the range of the western sandpiper Calidris mauri. First, we developed a winter isotope basemap from stable-hydrogen (dD), -carbon (d13C), and -nitrogen (d15N) isotopes of feathers grown in wintering areas. dD and d15N values from wintering individuals varied with the latitude and longitude of capture location, while d13C varied with longitude only. We then tested the ability of the basemap to assign known-origin individuals. Sixty percent of wintering individuals were correctly assigned to their region of origin out of seven possible regions. Finally, we estimated the winter origins of breeding and migrant individuals and compared the resulting empirical distribution against the distribution that would be expected based on patterns of winter relative abundance. For breeding birds, the distribution of winter origins differed from expected only among males in the Yukon-Kuskokwim (Y-K) Delta and Nome, Alaska. Males in the Y-K Delta originated overwhelmingly from western Mexico, while in Nome, there were fewer males from western North America and more from the Baja Peninsula than expected. An unexpectedly high proportion of migrants captured at a stopover site in the interior United States originated from eastern and southern wintering areas, while none originated from western North America. In general, we document substantial mixing between the breeding and wintering populations of both sexes, which will buffer the global population of western sandpipers from the effects of local habitat loss on both breeding and wintering grounds. DOI
130. Jonker, RM; Kurvers, RHJM; van de Bilt, A; Faber, M; Van Wieren, SE; Prins, HHT; Ydenberg, RC. (2012) Rapid adaptive adjustment of parental care coincident with altered migratory behaviour.Evolutionary Ecology 26: 657-667 Rapid adaptive adjustment of parental care coincident with altered migratory behaviour
Barnacle geese; Parent-offspring conflict; Migration; Life-history evolution; Branta leucopsis; Colonization
The optimal duration of parental care is shaped by the trade-off between investment in current and expected future reproductive success. A change in migratory behaviour is expected to affect the optimal duration of parental care, because migration and non-migration differ in expectations of future reproductive success as a result of differential adult and/or offspring mortality. Here we studied how a recent emergence of non-migratory behaviour has affected the duration of parental care in the previously (until the 1980s) strictly migratory Russian breeding population of the barnacle geese Branta leucopsis. As a measure of parental care, we compared the vigilance behaviour of parents and non-parents in both migratory and non-migratory barnacle geese throughout the season. We estimated the duration of parental care at 233 days for migratory and 183 days for non-migratory barnacle geese. This constitutes a shortening of the duration of parental care of 21% in 25 years. Barnacle geese are thus able to rapidly adapt their parental care behaviour to ecological conditions associated with altered migratory behaviour. Our study demonstrates that a termination of migratory behaviour resulted in a drastic reduction in parental care and highlights the importance of studying the ecological and behavioural consequences of changes in migratory behaviour and the consequences of these changes for life-history evolution. DOI
129. Kraus, RHS; Kerstens, HHD; van Hooft, P; Megens, HJ; Elmberg, J; Tsvey, A; Sartakov, D; Soloviev, SA; Crooijmans, RPMA; Groenen, MAM; Ydenberg, RC; Prins, HHT. (2012) Widespread horizontal genomic exchange does not erode species barriers among sympatric ducks.BMC Evolutionary Biology 12 Widespread horizontal genomic exchange does not erode species barriers among sympatric ducks
MALLARDS ANAS-PLATYRHYNCHOS; MULTILOCUS GENOTYPE DATA; LINKAGE DISEQUILIBRIUM; POPULATION-STRUCTURE; PHYLOGENETIC-RELATIONSHIPS; HYBRIDIZATION PATTERNS; FINITE POPULATION; MIOCENE CLIMATE; WATERFOWL AVES; AVERAGE NUMBER
Background: The study of speciation and maintenance of species barriers is at the core of evolutionary biology. During speciation the genome of one population becomes separated from other populations of the same species, which may lead to genomic incompatibility with time. This separation is complete when no fertile offspring is produced from inter-population matings, which is the basis of the biological species concept. Birds, in particular ducks, are recognised as a challenging and illustrative group of higher vertebrates for speciation studies. There are many sympatric and ecologically similar duck species, among which fertile hybrids occur relatively frequently in nature, yet these species remain distinct. Results: We show that the degree of shared single nucleotide polymorphisms (SNPs) between five species of dabbling ducks (genus Anas) is an order of magnitude higher than that previously reported between any pair of eukaryotic species with comparable evolutionary distances. We demonstrate that hybridisation has led to sustained exchange of genetic material between duck species on an evolutionary time scale without disintegrating species boundaries. Even though behavioural, genetic and ecological factors uphold species boundaries in ducks, we detect opposing forces allowing for viable interspecific hybrids, with long-term evolutionary implications. Based on the superspecies concept we here introduce the novel term "supra-population" to explain the persistence of SNPs identical by descent within the studied ducks despite their history as distinct species dating back millions of years. Conclusions: By reviewing evidence from speciation theory, palaeogeography and palaeontology we propose a fundamentally new model of speciation to accommodate our genetic findings in dabbling ducks. This model, we argue, may also shed light on longstanding unresolved general speciation and hybridisation patterns in higher organisms, e. g. in other bird groups with unusually high hybridisation rates. Observed parallels to horizontal gene transfer in bacteria facilitate the understanding of why ducks have been such an evolutionarily successful group of animals. There is large evolutionary potential in the ability to exchange genes among species and the resulting dramatic increase of effective population size to counter selective constraints. DOI
128. Kurvers, RHJM; de Hoog, SIV; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2012) No evidence for negative frequency-dependent feeding performance in relation to personality.Behavioral Ecology 23: 51-57 No evidence for negative frequency-dependent feeding performance in relation to personality
barnacle goose; boldness; foraging strategy; negative frequency-dependent selection; personality; producer-scrounger game
An increasing number of studies report the presence of consistent individual differences in behavior and/or physiology over time and context, known as animal personality. A pivotal question in animal personality research concerns the mechanism(s) responsible for its evolution and maintenance. Negative frequency-dependent selection is considered to be one of these important mechanisms, although evidence for this is largely absent. Here, we studied whether the feeding performance of barnacle geese was negative frequency-dependent in a producer-scrounger game. We studied the feeding time of one bold or one shy individual in groups consisting of only bold or shy companions to study if the rare type in the group performs best. A previous study with this species showed that scrounging increased with shyness. Hence, we expected shy individuals to do better in the presence of bold companions due to the increased scrounging opportunity and bold individuals to do better in the presence of shy companions as there were ample opportunities to produce food. We found no evidence for negative frequency-dependent feeding success; rather, we found that, independent of their boldness score, all individuals enjoyed higher feeding success when foraging with bold than with shy companions. The higher foraging success of individuals foraging with bold companions is explained by a higher joining proportion in the presence of bold companions. Our results provide no evidence for negative frequency-dependent feeding success in barnacle geese but indicate that both bold and shy individuals can increase their foraging returns by associating with bold individuals. DOI
127. Kurvers, RHJM; Nolet, BA; Prins, HHT; Ydenberg, RC; van Oers, K. (2012) Boldness affects foraging decisions in barnacle geese: an experimental approach.Behavioral Ecology 23: 1155-1161 Boldness affects foraging decisions in barnacle geese: an experimental approach
boldness; foraging; joining; personality; social context; social facilitation
Individuals foraging in groups constantly need to make decisions, such as when to leave a group, when to join a group, and when to move collectively to another feeding site. In recent years, it has become evident that personality may affect these foraging decisions, but studies where individuals are experimentally forced into different roles are still absent. Here, we forced individual barnacle geese, Branta leucopsis, differing in boldness scores, either in a joining or in a leaving role in a feeding context. We placed a food patch at the far end of a test arena and measured the arrival latency and number of visits of individuals to the patch either in the presence of a companion that was confined near the food patch (joining context) or in the presence of a companion that was confined away from the food patch (leaving context). We also ran trials without a companion (nonsocial context). Bolder individuals arrived more quickly than shyer individuals in the leaving context, but there was no effect of boldness in the joining context, suggesting that boldness differences are important in explaining variation in leaving behavior but not in joining behavior. The difference in arrival latency between the joining and non-social context increased with decreasing boldness score, suggesting that shyer individuals are more responsive to the presence of other individuals (i.e., social facilitation). These results indicate that individual differences in boldness play a role in patch choice decisions of group-living animals, such as when to leave a flock and when to join others at a patch. DOI
126. Kuwae, T; Miyoshi, E; Hosokawa, S; Ichimi, K; Hosoya, J; Amano, T; Moriya, T; Kondoh, M; Ydenberg, RC; Elner, RW. (2012) Variable and complex food web structures revealed by exploring missing trophic links between birds and biofilm.Ecology Letters 15: 347-356 Variable and complex food web structures revealed by exploring missing trophic links between birds and biofilm
Behavioural ecology; feeding ecology; foraging behaviour; functional morphology; omnivory; phylogeny; tongue spine; trophic relationship; wader
Food webs are comprised of a network of trophic interactions and are essential to elucidating ecosystem processes and functions. However, the presence of unknown, but critical networks hampers understanding of complex and dynamic food webs in nature. Here, we empirically demonstrate a missing link, both critical and variable, by revealing that direct predator-prey relationships between shorebirds and biofilm are widespread and mediated by multiple ecological and evolutionary determinants. Food source mixing models and energy budget estimates indicate that the strength of the missing linkage is dependent on predator traits (body mass and foraging action rate) and the environment that determines food density. Morphological analyses, showing that smaller bodied species possess more developed feeding apparatus to consume biofilm, suggest that the linkage is also phylogenetically dependent and affords a compelling re-interpretation of niche differentiation. We contend that exploring missing links is a necessity for revealing true network structure and dynamics. DOI
125. Bos, D; Ydenberg, R. (2011) Evaluation of alternative management strategies of muskrat Ondatra zibethicus population control using a population model.Wildlife Biology 17: 143-155 Evaluation of alternative management strategies of muskrat Ondatra zibethicus population control using a population model
model; muskrat; Ondatra zibethicus; pest species; RAMAS-Metapop; trapping
Muskrats Ondatra zibethicus are considered a pest species in the Netherlands, and a year-round control programme is in effect. Currently, the agency responsible for the management of muskrat populations in the Netherlands (the LCCM) is preparing for field studies to compare alternative strategies of control. In order to decide on the specific design of such field studies, a population dynamic model was built. The model compares the current management strategy with alternatives in which the effort is focused in space or in time. The model allows us to prioritise future research questions. The major gaps in knowledge at this moment are: I) insight into the costs of harvesting at different harvest rates, and 2) the relationship between population density on the one hand and (financial damage or) safety risk on the other hand. We suggest continuing the current management, and to test our hypothesis that intensifying harvest will lead to lower numbers of animals killed in the medium term than more extensive harvest rates. The muskrat control programme offers excellent opportunities for applied biological studies of which the benefits are likely to outweigh the costs. DOI
124. Dekker, D; Dekker, I; Christie, D; Ydenberg, R. (2011) Do Staging Semipalmated Sandpipers Spend the High-Tide Period in Flight over the Ocean to Avoid Falcon Attacks along Shore?Waterbirds 34: 195-201 Do Staging Semipalmated Sandpipers Spend the High-Tide Period in Flight over the Ocean to Avoid Falcon Attacks along Shore?
CALIDRIS-PUSILLA; PEREGRINE FALCON; RAPTOR PREDATION; BRITISH-COLUMBIA; FALL MIGRATION; BOUNDARY BAY; DUNLINS; FUNDY; SELECTION; FLOCKING
The interaction of aerial predators and migrant Semipalmated Sandpipers (Calidris pusilla) was studied at Mary's Point in the upper Bay of Fundy, New Brunswick, Canada, during August of 2009 and 2010. Peregrine Falcons (Falco peregrinus) were locally reintroduced and increased from one active nest site in 1989 to 27 in 2010, which coincided with a decline of sandpipers roosting at Mary's Point from an annual mean of 161,000 in 1976-1982 to 15,000 or less during this study. Mean roosting time of flocks was 33 min (range = 10 to 40 min; N = 6). Sandpipers returned to the beach 1 h:36 min after high-tide (range = 1 h:10 to 2 h:13 min; N = 5), but were soon flushed again by falcons. On ten of 19 days, during part of the high-tide period, flocks of sandpipers remained in flight over the ocean. Termed Over-Ocean Flocking (OOF), this behavior was seen on days when spring tides inundated all beach habitat, and also at lower tides, which supports the hypothesis that OOF is an antipredator strategy intended to avoid surprise attacks by falcons near the shore. Raptors sighted during 128 hours afield included 226 Peregrines, 20 Merlins (Falco columbarius) and two Sharp-shinned Hawks (Accipiter striatus). At 1.0-3.2 Peregrine sightings/h(-1) (mean 1.8) the level of disturbance is high and supports the hypothesis that the decline in roosting sandpipers at Mary's Point is linked to predation danger. Received 11 December 2010, accepted 17 March 2011.
123. Hope, DD; Lank, DB; Smith, BD; Ydenberg, RC. (2011) Migration of two calidrid sandpiper species on the predator landscape: how stopover time and hence migration speed vary with geographical proximity to danger.Journal of Avian Biology 42: 522-529 Migration of two calidrid sandpiper species on the predator landscape: how stopover time and hence migration speed vary with geographical proximity to danger
WESTERN SANDPIPERS; BIRD MIGRATION; MARKED ANIMALS; TRADE-OFFS; SURVIVAL; MAURI; POPULATIONS; RISK; SITE; MINIMIZATION
The effects of relative fuel load on migration speed and on vulnerability have been investigated, but the effects of seasonal variation in predation danger on the amount of fuel and duration of stopover have not been considered. We analyzed seasonal patterns of stopover residence times for western and semipalmated sandpipers Calidris mauri and C. pusilla on southward migration in relation to the passage of migratory peregrine falcons Falco peregrinus. We predicted that individuals on stopover far in advance of the seasonal arrival of falcons would adjust stopover length and hence relative fuel load to migrate slowly and cautiously. We predicted that individuals on stopover later in the season would increase migratory speed as the arrival of migratory falcons came closer, while individuals on stopover under or behind the passage of falcons would migrate slowly. Adult and juvenile semipalmated and adult western sandpipers migrated prior to seasonal increases in peregrine abundance, and as predicted, the seasonal patterns of their stopover durations are consistent with an increase in the speed of migration as the date of peregrine arrival approached. Juvenile western sandpipers, in contrast, migrating concurrently with falcons, slowed their speed of migration as predator abundance increased. Stopover patterns differ between species due to different relative fuel loads. The results fit predictions made based on a mortality-minimizing migration strategy. DOI
122. Jonker, RM; Kuiper, MW; Snijders, L; Van Wieren, SE; Ydenberg, RC; Prins, HHT. (2011) Divergence in timing of parental care and migration in barnacle geese.Behavioral Ecology 22 Divergence in timing of parental care and migration in barnacle geese
adaptation; Branta leucopsis; bird migration; parental care; parent-offspring conflict
In migratory geese, the extended association of parents and offspring is thought to play a crucial role in culturally transmitting the migration strategy to the next generation. Goslings migrate with their parents and associate closely with them almost until the next breeding season. Families do not break up until spring migration, when the parent-offspring conflict intensifies during preparation for the next generation of offspring. Recently, the commencement of spring migration of the Russian population of the barnacle goose has been delayed by about 1 month. Here, we investigated whether the duration of parental care behavior changed with this alteration in migratory behavior. In contrast to our expectation, we found that parental care terminated well before the commencement of spring migration and that parent-offspring associations were nearly absent during spring migration. We argue that the mechanisms for determining the duration of parental care is different from that determining the commencement of spring migration; hence, we conclude that a divergence in timing has developed between both behaviors. A consequence of this divergence could be that the cultural transmission of migratory behavior is disrupted, possibly playing a role in the recent establishment of new populations of Barnacle geese across the Russian flyway. DOI
121. Kraus, RHS; van Hooft, P; Waldenstroem, J; Latorre-Margalef, N; Ydenberg, RC; Prins, HHT. (2011) Avian Influenza Surveillance with FTA Cards: Field Methods, Biosafety, and Transportation Issues Solved.J. Vis. Exp.Avian Influenza Surveillance with FTA Cards: Field Methods, Biosafety, and Transportation Issues Solved
Immunology; Issue 54; AI; Influenza A Virus; zoonoses; reverse transcription PCR; viral RNA; surveillance; duck trap; RNA preservation and storage; infection; mallard
Avian Influenza Viruses (AIVs) infect many mammals, including humans(1). These AIVs are diverse in their natural hosts, harboring almost all possible viral subtypes(2). Human pandemics of flu originally stem from AIVs(3). Many fatal human cases during the H5N1 outbreaks in recent years were reported. Lately, a new AIV related strain swept through the human population, causing the 'swine flu epidemic'(4). Although human trading and transportation activity seems to be responsible for the spread of highly pathogenic strains(5), dispersal can also partly be attributed to wild birds(6, 7). However, the actual reservoir of all AIV strains is wild birds. In reaction to this and in face of severe commercial losses in the poultry industry, large surveillance programs have been implemented globally to collect information on the ecology of AIVs, and to install early warning systems to detect certain highly pathogenic strains(8-12). Traditional virological methods require viruses to be intact and cultivated before analysis. This necessitates strict cold chains with deep freezers and heavy biosafety procedures to be in place during transport. Long-term surveillance is therefore usually restricted to a few field stations close to well equipped laboratories. Remote areas cannot be sampled unless logistically cumbersome procedures are implemented. These problems have been recognised(13, 14) and the use of alternative storage and transport strategies investigated (alcohols or guanidine) (15)-(17). Recently, Kraus et al. (18) introduced a method to collect, store and transport AIV samples, based on a special filter paper. FTA cards(19) preserve RNA on a dry storage basis(20) and render pathogens inactive upon contact(21). This study showed that FTA cards can be used to detect AIV RNA in reverse-transcription PCR and that the resulting cDNA could be sequenced and virus genes and determined. In the study of Kraus et al. (18) a laboratory isolate of AIV was used, and samples were handled individually. In the extension presented here, faecal samples from wild birds from the duck trap at the Ottenby Bird Observatory (SE Sweden) were tested directly to illustrate the usefulness of the methods under field conditions. Catching of ducks and sample collection by cloacal swabs is demonstrated. The current protocol includes upscaling of the work flow from single tube handling to a 96-well design. Although less sensitive than the traditional methods, the method of FTA cards provides an excellent supplement to large surveillance schemes. It allows collection and analysis of samples from anywhere in the world, without the need to maintaining a cool chain or safety regulations with respect to shipping of hazardous reagents, such as alcohol or guanidine. DOI PubMed
120. Kraus, RHS; Zeddeman, A; van Hooft, P; Sartakov, D; Soloviev, SA; Ydenberg, RC; Prins, HHT. (2011) Evolution and connectivity in the world-wide migration system of the mallard: Inferences from mitochondrial DNA.BMC Genetics 12 Evolution and connectivity in the world-wide migration system of the mallard: Inferences from mitochondrial DNA
DUCK ANAS-PLATYRHYNCHOS; INFLUENZA-A VIRUSES; AVIAN INFLUENZA; BIRD MIGRATION; POPULATION-STRUCTURE; NORTH-AMERICA; BLACK DUCKS; GENE FLOW; HYBRIDIZATION; PHILOPATRY
Background: Main waterfowl migration systems are well understood through ringing activities. However, in mallards (Anas platyrhynchos) ringing studies suggest deviations from general migratory trends and traditions in waterfowl. Furthermore, surprisingly little is known about the population genetic structure of mallards, and studying it may yield insight into the spread of diseases such as Avian Influenza, and in management and conservation of wetlands. The study of evolution of genetic diversity and subsequent partitioning thereof during the last glaciation adds to ongoing discussions on the general evolution of waterfowl populations and flyway evolution. Hypothesised mallard flyways are tested explicitly by analysing mitochondrial mallard DNA from the whole northern hemisphere. Results: Phylogenetic analyses confirm two mitochondrial mallard clades. Genetic differentiation within Eurasia and North-America is low, on a continental scale, but large differences occur between these two land masses (FST = 0.51). Half the genetic variance lies within sampling locations, and a negligible portion between currently recognised waterfowl flyways, within Eurasia and North-America. Analysis of molecular variance (AMOVA) at continent scale, incorporating sampling localities as smallest units, also shows the absence of population structure on the flyway level. Finally, demographic modelling by coalescence simulation proposes a split between Eurasia and North-America 43,000 to 74,000 years ago and strong population growth (similar to 100fold) since then and little migration (not statistically different from zero). Conclusions: Based on this first complete assessment of the mallard's world-wide population genetic structure we confirm that no more than two mtDNA clades exist. Clade A is characteristic for Eurasia, and clade B for NorthAmerica although some representatives of clade A are also found in North-America. We explain this pattern by evaluating competing hypotheses and conclude that a complex mix of historical, recent and anthropogenic factors shaped the current mallard populations. We refute population classification based on flyways proposed by ornithologists and managers, because they seem to have little biological meaning. Our results have implications for wetland management and conservation, with special regard to the release of farmed mallards for hunting, as well as for the possible transmission of Avian Influenza by mallards due to migration. DOI
119. Heath, JP; Gilchrist, HG; Ydenberg, RC. (2010) Interactions between rate processes with different timescales explain counterintuitive foraging patterns of arctic wintering eiders.Proceedings of the Royal Society B-Biological Sciences 277: 3179-3186 Interactions between rate processes with different timescales explain counterintuitive foraging patterns of arctic wintering eiders
foraging; diving; digestion; scale; time series; arctic ecology
To maximize fitness, animals must respond to a variety of processes that operate at different rates or timescales. Appropriate decisions could therefore involve complex interactions among these processes. For example, eiders wintering in the arctic sea ice must consider locomotion and physiology of diving for benthic invertebrates, digestive processing rate and a nonlinear decrease in profitability of diving as currents increase over the tidal cycle. Using a multi-scale dynamic modelling approach and continuous field observations of individuals, we demonstrate that the strategy that maximizes long-term energy gain involves resting during the most profitable foraging period (slack currents). These counterintuitive foraging patterns are an adaptive trade-off between multiple overlapping rate processes and cannot be explained by classical rate-maximizing optimization theory, which only considers a single timescale and predicts a constant rate of foraging. By reducing foraging and instead digesting during slack currents, eiders structure their activity in order to maximize long-term energetic gain over an entire tide cycle. This study reveals how counterintuitive patterns and a complex functional response can result from a simple trade-off among several overlapping rate processes, emphasizing the necessity of a multi-scale approach for understanding adaptive routines in the wild and evaluating mechanisms in ecological time series. DOI
118. Kurvers, R.H.J.M., H.H.T. Prins, S.E. van Wieren, K. van Oers, B.A. Nolet and R.C. Ydenberg. (2010) The effect of personality on social foraging: shy barnacle geese scrounge more.Proceedings of the Royal Society B-Biological Sciences 277: 601-608 The effect of personality on social foraging: shy barnacle geese scrounge more.
Animals foraging in groups can either search for food themselves (producing) or search for the food discoveries of other individuals (scrounging). Tactic use in producer-scrounger games is partly flexible but individuals tend to show consistency in tactic use under different conditions suggesting that personality might play a role in tactic use in producer-scrounger games. Here we studied the use of producing and scrounging tactics by bold and shy barnacle geese (Branta leucopsis), where boldness is a personality trait known to be repeatable over time in this species. We defined individuals as bold, shy or intermediate based on two novel object tests. We scored the frequency of finding food patches (the outcome of investing in producing) and joining patches (the outcome of investing in scrounging) by bold and shy individuals and their feeding time. Shy individuals had a higher frequency of joining than bold individuals, demonstrating for the first time that personality is associated with tactic use in a producer-scrounger game. Bold individuals tended to spend more time feeding than shy individuals. Our results highlight the importance of including individual behavioural variation in models of producer-scrounger games.
DOI
117. Kurvers, RHJM; van Oers, K; Nolet, BA; Jonker, RM; van Wieren, SE; Prins, HHT; Ydenberg, RC. (2010) Personality predicts the use of social information.Ecology Letters 13: 829-837 Personality predicts the use of social information
Barnacle goose; boldness; Branta leucopsis; personality; social information
P>The use of social information is known to affect various important aspects of an individual's ecology, such as foraging, dispersal and space use and is generally assumed to be entirely flexible and context dependent. However, the potential link between personality differences and social information use has received little attention. In this study, we studied whether use of social information was related to personality, using barnacle geese, Branta leucopsis, where boldness is a personality trait known to be consistent over time. We found that the use of social information decreased with increasing boldness score of the individuals. Individuals had lower feeding times when they did not follow the social information and this effect was unrelated to boldness score. When manipulating social information, thereby making it incorrect, individuals irrespective of their boldness score, learned that it was incorrect and ignored it. Our results show that social information use depends on the personality type of an individual, which calls for incorporation of these personality-related differences in studies of spatial distribution of animals in which social information use plays a role. DOI
116.Ydenberg, RC; Davies, WE. (2010) Resource geometry and provisioning routines.Behavioral Ecology 21: 1170-1178 Resource geometry and provisioning routines
central place foraging; delivery; provisioning; seabirds; self-feeding; solitary bees
Provisioners capture items both for delivery and for self-feeding. In doing so, they may travel directly to and from a single location, visit several patches on each excursion from a delivery point, or alternate excursions to different destinations. Prey suitable for self-feeding versus delivery have differing attributes, which means that they are often best sought in different places. Visiting separate patches to self-feed and to load prey for delivery requires more travel time than foraging for both types of prey at a single location, but both self-feeding and loading are faster if carried out in the most suitable patches. Here, we investigate how the distribution of different types of food resources around a central delivery point affects the routine with which a provisioner visits patches to forage. Our results show that each of several basic travel routines is best in some broad region of a parameter space that considers the loading time saved in relation to the extra travel time required. This framework provides a simple explanation for the variety of routines observed in nature and can additionally account for the circumstances under which provisioners concentrate loads for delivery by internal processing, known in some seabirds. DOI
115.Ydenberg, Ronald C.; Dekker, Dick; Kaiser, Gary; Shepherd, Philippa C.F.; Evans Ogden, Lesley; Rickards, Karen; Lank, David B. (2010) Winter body mass and over-ocean flocking as components of danger management by Pacific dunlins.BMC Ecology 10: 1-11 Winter body mass and over-ocean flocking as components of danger management by Pacific dunlins.
Background: We compared records of the body mass and roosting behavior of Pacific dunlins (Calidris alp/no pacifica) wintering on the Fraser River estuary in southwest British Columbia between the 1970s and the 1990s. 'Over-ocean flocking' is a relatively safe but energetically-expensive alternative to roosting during the high tide period. Fat stores offer protection against starvation, but are a liability in escape performance, and increase flight costs. Peregrine falcons (Falco peregrinus) were scarce on the Fraser River estuary in the 1970s, but their numbers have since recovered, and they prey heavily on dunlins. The increase has altered the balance between predation and starvation risks for dunlins, and thus how dunlins regulate roosting behavior and body mass to manage the danger. We therefore predicted an increase in the frequency of over-ocean flocking as well as a decrease in the amount of fat carried by dunlins over these decades. Results: Historical observations indicate that over-ocean flocking of dunlins was rare prior to the mid-1990s and became common thereafter. Residual body masses of dunlins were higher in the 1970s, with the greatest difference between the decades coinciding with peak peregrine abundance in October, and shrinking over the course of winter as falcon seasonal abundance declines. Whole-body fat content of dunlins was lower in the 1990s, and accounted for most of the change in body mass. Conclusions: Pacific dunlins appear to manage danger in a complex manner that involves adjustments both in fat reserves and roosting behavior. We discuss reasons why over-ocean flocking has apparently become more common on the Fraser estuary than at other dunlin wintering sites.
114. Blackburn, GS; Hipfner, JM; Ydenberg, RC. (2009) Evidence that tufted puffins Fratercula cirrhata use colony overflights to reduce kleptoparasitism risk.Journal of Avian Biology 40: 412-418 Evidence that tufted puffins Fratercula cirrhata use colony overflights to reduce kleptoparasitism risk
ATLANTIC PUFFINS; GREAT-ISLAND; ARCTICA L; PREDATION; SEABIRDS; SUCCESS; FLIGHT; GULLS; WIND; NEWFOUNDLAND
Predation, foraging and mating costs are critical factors shaping life histories. Among colonial seabirds, colony overflights may enhance foraging or mating success, or diminish the risk of predation and kleptoparasitism. The latter possibility is difficult to test because low predation or kleptoparasitism rates could be due either to low danger or to effective counter-tactics by prey. Tufted puffins Fratercula cirrhata breeding at a large colony in British Columbia, Canada, deliver several loads of fish each day to their nestlings and are targets for kleptoparasitism by glaucous-winged gulls Larus glaucescens. In the present study, we documented the ecological conditions under which overflights occurred in order to assess when overflights were made and to statistically isolate the effect of overflights on kleptoparasitism risk at this site. Load-carrying puffins engaged in overflights under ecological conditions associated with relatively high rates of kleptoparasitism. Further, when ecological factors determining risk were statistically controlled, overflights were correlated with marginally lower chances of kleptoparasitism than when the risk factors were ignored. The results suggest that breeding puffins at this site use overflights for kleptoparasite avoidance. This tactic is used sparingly, suggesting it is costly. Costs of overflight behaviour might contribute to the impact of kleptoparasitism on the breeding success of tufted puffins. DOI
113. Davies, WE; Hipfner, JM; Hobson, KA; Ydenberg, RC. (2009) Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids.Marine Ecology-Progress Series 382: 211-219 Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids
AUKLETS PTYCHORAMPHUS-ALEUTICUS; STABLE-ISOTOPES; TROPHIC RELATIONSHIPS; RHINOCEROS AUKLETS; BRITISH-COLUMBIA; TRIANGLE ISLAND; OCEAN CLIMATE; PISCIVOROUS SEABIRD; BREEDING SUCCESS; FORAGING AREAS
We measured delta N-15 and delta C-13 values in the blood of breeding adults and nestlings of 5 species of alcids at Triangle Island, British Columbia, to estimate the extent to which these seabirds alter their foraging ecology across successive breeding stages. Considerable intraspecific (stage-to-stage) and interspecific variation was found. Two species-common murre Uria aalge and pigeon guillemot Cepphus columba-fed consistently at high trophic levels (i.e. diets of fish) in inshore or benthically linked habitats. The foraging ecology of 3 others-Cassin's auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monocerata and tufted puffin Fratercula cirrhata-was more variable. Tufted puffins exhibited especially dramatic trophic and habitat shifts between early and late-season diets. With the exception of tufted puffin, the diet of provisioning adults differed from that. fed to their nestlings. Trophic level of the community as a whole increased as the season progressed due to the combination of trophic shifting by rhinoceros auklets and tufted Puffins, and earlier breeding by zooplanktivorous Cassin's auklets than by piscivorous murres and guillemots. Our results contribute to a growing body of evidence that marine bird species exhibit considerable flexibility in their foraging behaviour and also shed new light on seasonal patterns in the trophic relations within marine bird communities. DOI
111. Kurvers, RHJM; Eijkelenkamp, B; van Oers, K; van Lith, B; van Wieren, SE; Ydenberg, RC; Prins, HHT. (2009) Personality differences explain leadership in barnacle geese.Animal Behaviour 78: 447-453 Personality differences explain leadership in barnacle geese
RISK-TAKING BEHAVIOR; ZEBRA FINCHES; INDIVIDUAL-DIFFERENCES; REALIZED HERITABILITY; ANIMAL PERSONALITIES; AVIAN PERSONALITIES; PARUS-MAJOR; GREAT TITS; EXPLORATION; MOVEMENTS
Personality in animal behaviour describes the observation that behavioural differences between individuals are consistent over time and context. Studies of group-living animals show that movement order among individuals is also consistent over time and context, suggesting that some individuals lead and others follow. However, the relationship between leadership and personality traits is poorly studied. We measured several personality traits and leadership of individual barnacle geese, Branta leucopsis. We measured body size and scored the dominance of individuals living in a stable group situation before subjecting them to an open-field test, an activity test, a novel-object test, and a leadership test in which the order of the movement of individuals in pairs towards a feeding patch was scored. We found high repeatability for activity and novel-object scores over time. Leadership was strongly correlated with novel-object score but not with dominance rank, activity or exploration in an open field. These results provide evidence that leadership is closely related to some aspects of personality. Interestingly, an individual's arrival at the food patch was affected not only by the novel-object score of the focal individual, but also by the novel-object score of the companion individual, indicating that movement patterns of individuals living in groups are affected by the personality traits of other group members and suggesting that movement patterns of a group may be shaped by the mix of personality types present in the group. Crown Copyright (C) 2009 Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved. DOI
110. LeBourdais, SV; Ydenberg, RC; Esler, D. (2009) Fish and harlequin ducks compete on breeding streams.Canadian Journal of Zoology-Revue Canadienne de Zoologie 87: 31-40 Fish and harlequin ducks compete on breeding streams
PREDATOR-PREY INTERACTIONS; LESSER SCAUP; FOOD; RESPONSES; IMPACT; RISK; METAANALYSIS; RECRUITMENT; COMMUNITY; SCULPINS
We investigated interactions among harlequin ducks (Histrionicus histrionicus ( L., 1758)), fish, and their shared aquatic insect prey. We measured flow variability, benthic aquatic prey abundance, fish presence, and breeding density of harlequins on eight rivers in the Southern Coast Mountain Range in British Columbia, Canada, in 2003 and 2004. Rivers with lower flow variability had higher abundance of aquatic insects. Densities of harlequins and fish presence on the rivers were both significantly and positively related to insect abundance, but path analysis revealed a strong negative correlation between them. We interpret this as an indirect interaction between harlequins and fish mediated by anti-predator behaviour of insects in the presence of fish, which reduces insect availability, rather than as a reduction in the abundance of aquatic insects through consumption by fishes. We hypothesize that the ongoing and widespread introduction of fish into historically fishless waters throughout North America may have contributed to the current low productivity and recruitment measured in populations of harlequins by reducing quality of breeding habitat. DOI
109. Pomeroy, A.C., D.A. Acevedo Seaman, R.W. Butler, R.W. Elner, T.D. Williams and R.C. Ydenberg. (2008) Feeding-danger tradeoffs underlie stopover site selection by migrants.Avian Conservation and Ecology - Écologie et Conservation des Oiseaux 3(1): 7 Feeding-danger tradeoffs underlie stopover site selection by migrants.
To migrate successfully, birds need to store adequate fat reserves to fuel each leg of the journey. Migrants acquire their fuel reserves at stopover sites; this often entails exposure to predators. Therefore, the safety attributes of sites may be as important as the feeding opportunities. Furthermore, site choice might depend on fuel load, with lean birds more willing to accept danger to obtain good feeding. Here, we evaluate the factors underlying stopover-site usage by migrant Western Sandpipers (Calidris mauri) on a landscape scale. We measured the food and danger attributes of 17 potential stopover sites in the Strait of Georgia and Puget Sound region. We used logistic regression models to test whether food, safety, or both were best able to predict usage of these sites by Western Sandpipers. Eight of the 17 sites were used by sandpipers on migration. Generally, sites that were high in food and safety were used, whereas sites that were low in food and safety were not. However, dangerous sites were used if there was ample food abundance, and sites with low food abundance were used if they were safe. The model including both food and safety best-predicted site usage by sandpipers. Furthermore, lean sandpipers used the most dangerous sites, whereas heavier birds (which do not need to risk feeding in dangerous locations) used safer sites. This study demonstrates that both food and danger attributes are considered by migrant birds when selecting stopover sites, thus both these attributes should be considered to prioritize and manage stopover sites for conservation.Website
108. Pomeroy, AC; Seaman, DAA; Butler, RW; Elner, RW; Williams, TD; Ydenberg, RC. (2008) Feeding-Danger Trade-Offs Underlie Stopover Site Selection by Migrants.Avian Conserv. Ecol. 3 Feeding-Danger Trade-Offs Underlie Stopover Site Selection by Migrants
Calidris mauri; food abundance; migration; predation danger; stopover site conservation; trade-off hypothesis; Western Sandpiper
To migrate successfully, birds need to store adequate fat reserves to fuel each leg of the journey. Migrants acquire their fuel reserves at stopover sites; this often entails exposure to predators. Therefore, the safety attributes of sites may be as important as the feeding opportunities. Furthermore, site choice might depend on fuel load, with lean birds more willing to accept danger to obtain good feeding. Here, we evaluate the factors underlying stopover-site usage by migrant Western Sandpipers (Calidris mauri) on a landscape scale. We measured the food and danger attributes of 17 potential stopover sites in the Strait of Georgia and Puget Sound region. We used logistic regression models to test whether food, safety, or both were best able to predict usage of these sites by Western Sandpipers. Eight of the 17 sites were used by sandpipers on migration. Generally, sites that were high in food and safety were used, whereas sites that were low in food and safety were not. However, dangerous sites were used if there was ample food abundance, and sites with low food abundance were used if they were safe. The model including both food and safety best-predicted site usage by sandpipers. Furthermore, lean sandpipers used the most dangerous sites, whereas heavier birds (which do not need to risk feeding in dangerous locations) used safer sites. This study demonstrates that both food and danger attributes are considered by migrant birds when selecting stopover sites, thus both these attributes should be considered to prioritize and manage stopover sites for conservation.
107. Worcester, R; Ydenberg, R. (2008) Cross-continental patterns in the timing of southward Peregrine Falcon migration in North America.J. Raptor Res. 42: 13-19 Cross-continental patterns in the timing of southward Peregrine Falcon migration in North America
Peregrine Falcon; Falco peregrinus; cross-continent; hawkwatch; migration; timing
We analyzed the timing of southward migration of Peregrine Falcons (Falco peregrinus) across North America, based on passage data compiled by the Hawk Migration Association of North America, supplemented with two other similar datasets collected by individual observers at sites in western Canada. The results show two distinct continental-scale patterns. First, the north to south progression of peak peregrine passage down the continent is readily apparent, occurring primarily during September and October. Second, the movement of Peregrine Falcons is earlier by 4-6 wk on the west coast than on the eastern seaboard, and is intermediate at inland sites. The wavefront of Peregrine Falcons advancing southward is oriented from southwest to northeast across the North American continent. We hypothesize that these patterns have implications for the southward migrations of potential prey species, which may select routes or times to avoid places of high risk due to Peregrine Falcons. DOI
106. Addison, B; Ydenberg, RC; Smith, BD. (2007) Tufted puffins (Fratercula cirrhata) respond to predation danger during colony approach flights.Auk 124: 63-70 Tufted puffins (Fratercula cirrhata) respond to predation danger during colony approach flights
Fratercula cirrhata; predation; raptor; synchrony; Tufted Puffin; wheeling
In spite of their putative importance in the evolution of certain traits (e.g., nocturnality, coloniality, cliff nesting), the effects of aerial predators on behavior of adult seabirds at colonies have been poorly investigated. We hypothesized that Tufted Puffins (Fratercula cirrhata) respond to danger posed by aerial predators by modifying their behavior to mitigate danger. We observed Tufted Puffins making repeated colony fly-ins and departures and characterized (1) the timing of this behavior, (2) the activity rate (number of birds arriving or departing), and (3) the risk-level of activity, with respect to predation danger posed by Bald Eagles (Haliaeetus leucocephalus) and Peregrine Falcons (Falco percgrinus). As we predicted, we found that Tufted Puffins (1) dilute danger by synchronizing their fly-in and departure activities, (2) reduce fly-in and departure activity rates when predators are present, and (3) switch to lower-risk fly-in activities (e.g., staying over water where they have an escape route from an aerial attack) when predators are present. Received 15 October 2004, accepted 5 January 2006.Website
104. Heath, JP; Gilchrist, HG; Ydenberg, RC. (2007) Can dive cycle models predict patterns of foraging behaviour? Diving by common eiders in an Arctic polynya.Animal Behaviour 73: 877-884 Can dive cycle models predict patterns of foraging behaviour? Diving by common eiders in an Arctic polynya
common eider; foraging theory; rate constraints; Somateria mollissima sedentaria; temporal scale
There has been wide empirical and theoretical interest in how diving animals allocate time between obtaining oxygen at the surface and foraging at depth. Assuming diminishing returns in oxygen gain at the surface, classic diving models predict that time on the surface should increase, while time spent foraging at depth should first increase and then decrease as travel time increases. Controlled laboratory experiments have indicated partial support for predictions of diving models; however, their usefulness in understanding patterns of diving behaviour in the wild is still in question. We assessed the applicability of diving models to foraging patterns of common elders, Somateria mollissima sedentaria, wintering in the Canadian Arctic. Underwater footage was used to quantify time foraging at depth and duration of surface pauses in relation to changes in travel time induced by strong tidal currents. Consistent with predictions of diving models, bottom foraging time decreased with increasing travel time, while total dive duration was relatively constant at 58.47 +/- 5.32 s, close to the estimated aerobic dive limit for this species. However, durations of surface pauses were not associated with diving parameters, as anticipated from diving models. Durations of surface pauses were highly variable (183.05 +/- 158.06 s) and often considerably longer than necessary to replenish oxygen stores. While the duration of surface pauses predicted by diving models in relation to travel time may be an optimal strategy when obtaining oxygen at the surface is the predominant constraint to foraging, a variety of processes operating at different timescales can influence behavioural patterns in the wild. Preliminary analysis considering the rate of digestive processing suggests that foraging patterns of eiders could be simultaneously influenced by several different rate constraints. Therefore, while static modelling approaches are an important heuristic tool for elucidating mechanisms underlying diving behaviour, dynamic approaches, which can incorporate variables concerning multiple physiological and environmental states, will probably be required to fully understand complex foraging patterns observed in the wild. 2007 The Association for the study of Animal Behaviour. Published by Elsevier Ltd. DOI
103. Norris, DR; Lank, DB; Pither, J; Chipley, D; Ydenberg, RC; Kyser, TK. (2007) Trace element profiles as unique identifiers of western sandpiper (Calidris mauri) populations.Canadian Journal of Zoology-Revue Canadienne de Zoologie 85: 579-583 Trace element profiles as unique identifiers of western sandpiper (Calidris mauri) populations
Understanding the ecology and evolution of migratory animals requires information on how populations are geographically linked between periods of the annual cycle. To examine whether trace elements could be used to track migratory birds, we analyzed concentrations of 42 trace elements in feathers of western sandpipers (Calidris mauri (Cabanis, 1857)) that were grown at five different wintering sites ranging from San Francisco Bay (USA) to the Bay of Panama. Linear discriminant analysis of 15 elements correctly classified all 26 individuals to their wintering sites, including two sites that were separated by less than 3 km. A randomization procedure confirmed the robustness of these findings. Our analysis suggests that trace elements can be used to assign individuals to specific sites of origin. Although we did not sample feathers from all wintering areas, the regions our sites represented comprised a significant percentage of the global population. However, since trace element profiles appear to be highly specific to geographic sites, we suggest that this technique is best suited for cases where samples can be obtained from the majority of populations throughout a species range. Thus, under certain circumstances, trace element profiles may provide the potential to identify populations with a high degree of spatial accuracy. DOI
102. Ost, M; Clark, CW; Kilpi, M; Ydenberg, R. (2007) Parental effort and reproductive skew in coalitions of brood rearing female common eiders.American Naturalist 169: 73-86 Parental effort and reproductive skew in coalitions of brood rearing female common eiders
parental effort; parental care game; body condition; vigilance; Somateria mollissima; Nash bargaining game
Members of breeding groups face conflicts over parental effort when balancing antipredatory vigilance and feeding. Empirical evidence has shown disparate responses to manipulations of parental effort. We develop a model in which we determine the evolutionarily stable effort of partners given their body conditions, allowing the benefits of shared care to be unevenly divided, and we test this model's predictions with data on common eiders (Somateria mollissima). Eiders show uniparental female care; females may share brood rearing, or they may tend alone, and their body condition at hatching of the young shows large environmentally induced variation. The model predicts that parental effort (vigilance) in a coalition is lower than when tending alone, controlling for parental condition; this prediction is supported by the data. The parental effort in a coalition should be positively correlated with body condition, and this prediction is also supported. Finally, parental effort should increase when partner condition decreases and vice versa; this prediction is partially supported. The Nash bargaining game may provide promising avenues by which to determine the precise settlement of reproductive skew and effort between coalition partners in the future.PDF
101. Peterson, JH; Roitberg, BD; Ydenberg, RC. (2007) When nesting involves two sequential, mutually exclusive activities: what's a mother to do?Evolutionary Ecology Research 9: 1187-1197 When nesting involves two sequential, mutually exclusive activities: what's a mother to do?
dynamic state variable model; Hymenoptera; nest provisioning decisions; offspring sex ratio; resource allocation; solitary bee
Background: Parents can invest in offspring through a variety of behaviours, some of which trade off against each other, such as investment in the current brood versus investment in a future one. Question: When should hymenopteran parents stop provisioning the current nest and decide whether to seal the entrance to the nest (e.g. with a number of leaf pieces)? Method and key assumptions: A dynamic state variable model. We assume that mothers alter reproductive decisions based on their perception of costs and benefits of brood cell and nest construction. Some of these construction behaviours allocate investment at one or a few offspring in a brood but others affect the entire brood. Conclusions: Several factors impact the decisions of when to cease provisioning new offspring and whether to seal the nest. Higher current nest value and greater risk of mortality increase the likelihood of both ceasing provisioning earlier and sealing the nest. The greater the benefit of sealing, either because of increased benefits or decreased negative impacts, the earlier and the more frequently it occurs.
100. Stephens, D.W., J. Brown and R.C. Ydenberg. (2007) Foraging.University of Chicago Press. 576 p. Foraging
98.Ydenberg, R.C. (2007) Provisioning.In: Foraging, Stephens, D.W., J. Brown and R.C. Ydenberg, Eds., Pp. 273-303. Chicago: University of Chicago Press.Provisioning.
97.Ydenberg, R.C., D.W. Stephens and J. Brown. (2007) Foraging: an overview.In: Foraging, Stephens, D.W., J. Brown and R.C. Ydenberg, Eds., Pp. 1-28. Chicago: University of Chicago Press.Foraging: an overview.
95. Bin Muzaffar, S; Ydenberg, RC; Jones, IL. (2006) Avian influenza: An ecological and evolutionary perspective for waterbird scientists.Waterbirds 29: 243-257 Avian influenza: An ecological and evolutionary perspective for waterbird scientists
avian influenza; avian flu; ecology; evolution; influenza A; HPAI; LPAI; H5N1; waterbirds
Highly pathogenic avian influenza (HPAI) type A of the subtype H5N1 has recently spread widely and rapidly across Eurasia, and even to Africa, with deaths of both wild and domestic birds recorded. There are fears that it may soon spread to the Americas. Media accounts, communications from international bodies and national governments, and even some of the professional research literature attributes the spread, in part, to movements of HP strains by migratory birds. The origin of highly pathogenic strains is attributed to mutations, or to reassortment of virus genes from different host species. In this paper we review these hypotheses in light of knowledge about the ecology and evolution of avian influenza, looked at from the viewpoint of its natural reservoir - waterbirds. Our purpose here is to alert waterbird biologists that they have much to contribute to the science of this globally-important issue. New technologies have revealed that the genome of avian influenza contains much variation beyond that recognizable by classical antibody techniques, and have established avian influenza as a rapidly evolving and diversifying lineage. The extensive genetic variability in the viral genome and extensive reassortment within host species Suggests that high pathogenicity could repeatedly and independently evolve from low pathogenic ancestors under appropriate selection pressures, such as those in poultry production systems. This makes infection of wild birds by HPAI lineages evolved in poultry a more likely occurrence than the reverse. The available evidence largely fits this model. We make recommendations that will help reduce the incursion of domestically-evolved avian influenza strains into wild populations of birds.
94. Heath, JP; Gilchrist, HG; Ydenberg, RC. (2006) Regulation of stroke pattern and swim speed across a range of current velocities: diving by common eiders wintering in polynyas in the Canadian Arctic.J Exp Biol 209: 3974-3983 Regulation of stroke pattern and swim speed across a range of current velocities: diving by common eiders wintering in polynyas in the Canadian Arctic
current; diving; swimming; wing stroke; glide; biomechanics; locomotion; drag; foot propulsion; underwater video
Swim speed during diving has important energetic consequences. Not only do costs increase as drag rises non-linearly with increasing speed, but speed also affects travel time to foraging patches and therefore time and energy budgets over the entire dive cycle. However, diving behaviour has rarely been considered in relation to current velocity. Strong tidal currents around the Belcher Islands, Nunavut, Canada, produce polynyas, persistent areas of open water in the sea ice which are important habitats for wildlife wintering in Hudson Bay. Some populations of common eiders Somateria mollissima sedentaria remain in polynyas through the winter where they dive to forage on benthic invertebrates. Strong tidal currents keep polynyas from freezing, but current velocity can exceed 1.5 m s(-1) and could influence time and energy costs of diving and foraging. Polynyas therefore provide naturally occurring flume tanks allowing investigation of diving strategies of free ranging birds in relation to current velocity. We used a custom designed sub-sea ice camera to non-invasively investigate over 150 dives to a depth of 11.3 m by a population of approximately 100 common eiders at Ulutsatuq polynya during February and March of 2002 and 2003. Current speed during recorded dives ranged from 0 to 1 m s(-1). As currents increased, vertical descent speed of eiders decreased, while descent duration and the number of wing strokes and foot strokes during descent to the bottom increased. However, nearly simultaneous strokes of wings and feet, and swim speed relative to the moving water, were maintained within a narrow range (2.28 +/- 0.23 Hz; 1.25 +/- 0.14 m s(-1), respectively). This close regulation of swim speed over a range in current speed of 1.0 m s(-1) might correspond to efficient muscle contraction rates, and probably reduces work rates by avoiding rapidly increasing drag at greater speeds; however, it also increases travel time to benthic foraging patches. Despite regulation of average swim speed, high instantaneous speeds during oscillatory stroking can increase dive costs due to drag. While most diving birds have been considered either foot or wing propelled, eider ducks used both wing and foot propulsion during descent. Our observations indicate that the power phase of foot strokes coincides with the transition between upstroke and downstroke of the wings, when drag is greatest. Coordinated timing between foot and wing propulsion could therefore serve to maintain a steadier speed during descent and decrease the costs of diving. Despite tight regulation of stroke and swim speed patterns, descent duration and total number of foot and wing strokes during descent increase non-linearly with increasing current velocity, suggesting an increase in energetic costs of diving.
93. Niehaus, AC; Ydenberg, RC. (2006) Ecological factors associated with the breeding and migratory phenology of high-latitude breeding western sandpipers.Polar Biology 30: 11-17 Ecological factors associated with the breeding and migratory phenology of high-latitude breeding western sandpipers
Environmental conditions influence the breeding and migratory patterns of many avian species and may have particularly dramatic effects on long-distance migrants that breed at northern latitudes. Environment, however, is only one of the ecological variables affecting avian phenology, and recent work shows that migration tactics may be strongly affected by changes in predator populations. We used long-term data from 1978 to 2000 to examine the interactions between snowmelt in western Alaska in relation to the breeding or migration phenologies of small shorebirds and their raptor predators. Although the sandpipers' time of arrival at Alaskan breeding sites corresponded with mean snowmelt, late snowmelts did delay breeding. These delays, however, did not persist to southward migration through British Columbia, likely due to the birds' ability to compensate for variance in the length of the breeding season. Raptor phenology at an early stopover site in British Columbia was strongly related to snowmelt, so that in years of early snowmelt falcons appeared earlier during the sandpipers' southbound migration. These differential effects indicate that earlier snowmelt due to climate change may alter the ecological dynamics of the predator-prey system. DOI
92. Pomeroy, AC; Butler, RW; Ydenberg, RC. (2006) Experimental evidence that migrants adjust usage at a stopover site to trade off food and danger.Behav Ecol 17: 1041-1045 Experimental evidence that migrants adjust usage at a stopover site to trade off food and danger
food abundance; migration; predation danger; stopover site usage; trade-off hypothesis; western sandpiper
Rich habitats, intensive feeding, and large fuel deposits are assumed to improve the capability for long-distance migration by birds but may also heighten their vulnerability or exposure to predators. Studies of habitat use by migrants have emphasized the importance of feeding, and relatively few studies have considered how migrants manage the dangers inherent in acquiring and storing fuel. Migrant western sandpipers (Calidris mauri) stop over on coastal mudflats characterized by a strong feeding-danger gradient, with both food and danger decreasing with distance from the shoreline. We experimentally manipulated danger by adding obstructive cover and measured sandpiper usage along this gradient. We compared sandpiper usage along a transect extending 100 m on either side of the obstruction with that on matched control transects without obstructions. The dropping density accumulated during a low-tide period provided a sensitive measure of sandpiper usage. Mean usage on control transects was 2.3 droppings/m(2) and was lower by 1.5 droppings/m(2) (65%) on treatment transects. Usage did not differ between control and treatment transects at the furthest distances from the obstruction, the difference increased with proximity to the obstruction, and was greater by on average 0.9 droppings/m(2) on the oceanward side (low food abundance) than on the shoreward side (high food abundance). All these findings were predicted by danger management theory. Our study provides experimental evidence that migrant birds are sensitive to danger on stopover and has implications for understanding migration strategies.
91. Nebel, S; Ydenberg, R. (2005) Differential predator escape performance contributes to a latitudinal sex ratio cline in a migratory shorebird.Behavioral Ecology and Sociobiology 59: 44-50 Differential predator escape performance contributes to a latitudinal sex ratio cline in a migratory shorebird
differential migration; mortality risk; predation danger; sex ratio cline; western sandpiper
Sexual segregation outside the mating season is common in vertebrates, and has been attributed to sexual differences in predator escape performance in ungulates and fish, but not in birds. Here, we tested the hypothesis that sex- and latitude-specific predator escape performance underlies the differential nonbreeding distribution of western sandpipers (Calidris mauri), a migratory shorebird. Females overwinter further south along the American Pacific coast, creating a latitudinal cline in sex ratio. Escape performance is reduced with increasing body mass, and birds generally carry less fat further south. Western sandpipers with poor escape performance were therefore predicted to prefer southern sites to reduce the risk of mortality posed by predators. Data from four nonbreeding latitudes showed that wing loading, used as an index of escape performance, was overall higher for females, and that it decreased with latitude in both sexes. Within latitudes, wing loading was lower at smaller, and presumably more dangerous, sites. Flight response to a predatory attack was longer in the south. Mortality risk offers a novel and candidate explanation for differential distribution patterns in western sandpipers and possibly other avian migrants.
90.Ydenberg, RC; Niehaus, AC; Lank, DB. (2005) Interannual differences in the relative timing of southward migration of male and female western sandpipers (Calidris mauri).Naturwissenschaften 92: 332-335 Interannual differences in the relative timing of southward migration of male and female western sandpipers (Calidris mauri)
In the shorebird subfamily Calidridinae, one of the parents shortens parental care and initiates southward migration before the other. We estimated the difference in passage date between male and female western sandpipers (Calidris mauri) at their first major stopover on the southward migration from breeding areas in Alaska, in 18 years between 1978 and 2000. Overall, adult females preceded adult males by 1.22 days. A novel finding was that among juveniles, which migrate approximately a month later than adults, females preceded males by similar magnitude (1.14 days). There was wide variation among years, however, and males actually preceded females in years with late hatch. We relate these findings to hypotheses for female-first southward migration in sandpipers.
89. Birmingham, AL; Hoover, SE; Winston, ML; Ydenberg, RC. (2004) Drifting bumble bee (Hymenoptera : Apidae) workers in commercial greenhouses may be social parasites.Canadian Journal of Zoology-Revue Canadienne de Zoologie 82: 1843-1853 Drifting bumble bee (Hymenoptera : Apidae) workers in commercial greenhouses may be social parasites
Commercial greenhouses require high densities of managed bumble bee (Bombus occidentalis Greene, 1858 and Bombus impatiens Cresson, 1863) colonies to pollinate crops such as tomatoes (Lycopersicon esculentum Miller). We examined drifting, a behavioural consequence of introducing closely aggregated colonies into greenhouse habitats, to determine possible explanations for observed drifting frequencies. Bee drift is normally associated with increased individual mortality and disease transfer between colonies. In this study, individual bees frequently drifted into and remained within foreign colonies. More drifting bees were found in colonies with higher worker and brood populations and greater pollen stores. Increased intracolony aggressive interactions were not associated with a higher number of drifting bees. Drifting bees had a significantly greater number of mature eggs in their ovaries than did resident worker bees residing in colonies hosting drifters, suggesting that drifting could potentially increase the fitness of individual worker bees and may not be solely a function of disorientation and (or) nectar robbing. Taken together, our results suggest that drifting of workers into foreign colonies within greenhouses may demonstrate a predisposition to social parasitism. This selfish worker reproduction challenges our previous understanding of social insect societies as being cooperative societies.
88. Dekker, D; Ydenberg, R. (2004) Raptor predation on wintering Dunlins in relation to the tidal cycle.Condor 106: 415-419 Raptor predation on wintering Dunlins in relation to the tidal cycle
Calidris alpina; Dunlin; Falco peregrinus; Peregrine falcon; raptor predation; tidal cycle
At Boundary Bay, British Columbia, Canada, Peregrine Falcons (Falco peregrinus) captured 94 Dunlins (Calidris alpina) in 652 hunts. The two main hunting methods were open attacks on flying Dunlins (62%) and stealth attacks on roosting or foraging Dunlins (35%). Peregrines hunted throughout the day, yet the kill rate per observation hour dropped 1-2 hr before high tide and peaked 1-2 hr after high tide. The drop in kill rate coincided with the departure of the mass of Dunlins for over-ocean flights lasting 2-4 hr. The peak in kill rate occurred just after the tide began to ebb and the Dunlins returned to forage in the shore zone. The hypothesis that closeness to shoreline vegetation is dangerous for Dunlins is supported by three converging lines of evidence: (1) the high success rate (44%) of peregrine hunts over the shore zone compared to the rate (11%) over tide flats and ocean; (2) the high kill rate per observation hour at high tide; and (3) the positive correlation of kill rate with the height of the tides. Seven of 13 Dunlins killed by Merlins (Falco columbarius) and all five Dunlins killed by Northern Harriers (Circus cyaneus) were also captured in the shore zone.
87.Ydenberg, RC; Butler, RW; Lank, DB; Smith, BD; Ireland, J. (2004) Western sandpipers have altered migration tactics as peregrine falcon populations have recovered.Proceedings of the Royal Society of London Series B-Biological Sciences 271: 1263-1269 Western sandpipers have altered migration tactics as peregrine falcon populations have recovered
predation danger; sandpiper migration tactics; stopovers; falcon population recovery; migration
The presence of top predators can affect prey behaviour, morphology and life history, and thereby can produce indirect population consequences greater and further reaching than direct depredation would have alone. Raptor species in the Americas are recovering since restrictions on the use of dichlorodiphenyl-trichloroethane (DDT) and the implementation of conservation measures, in effect constituting a hemisphere-wide predator-reintroduction experiment, and profound effects on populations of their prey are to be expected. Here, we document changes in the behaviour of western sandpipers (Calidris mauri) at migratory stopover sites over two decades. Since 1985, migratory body mass and stopover durations of western sandpipers have fallen steadily at some stopovers in the Strait of Georgia, British Columbia. Comparisons between years, sites and seasons strongly implicate increasing danger from the recovery of peregrine falcons (Falco peregrinus) as a causal factor. A decade-long ongoing steep decline in sandpiper numbers censused on our study site is explained entirely by the shortening stopover duration, rather than fewer individuals using the site. Such behavioural changes are probably general among migratory shorebird species, and may be contributing to the widespread census declines reported in North America.
86. Lank, DB; Butler, RW; Ireland, J; Ydenberg, RC. (2003) Effects of predation danger on migration strategies of sandpipers.Oikos 103: 303-319 Effects of predation danger on migration strategies of sandpipers
We examine the potential selective importance of predation danger on the evolution of migration strategies of arctic-breeding calidrid sandpipers. Adult calidrids truncate parental care for reasons not obviously related to levels of food abundance on the breeding areas or at migratory stopover sites, suggesting that a different trade-off occurs between providing additional care and adult survivorship. The southward migrations of adult western sandpipers precede those of migratory peregrine falcons by almost a month. By moving early and quickly, adults remain ahead of migrant falcons all the way to their non-breeding areas, where they rapidly moult flight feathers. They complete the moult just as falcons arrive in late September-October. By migrating early, they avoid exposure to falcons when they are unusually vulnerable, due to the requirements for fuelling migratory flight and of wing feather moult. Juvenile western sandpipers migrate south just as falcon numbers start to increase, but do not moult flight feathers in their first winter. Pacific dunlin use an alternative strategy of remaining and moulting in Alaska after falcons depart, and migrating to their overwintering sites after migrants have passed. East of the Rocky Mountains, the southbound migration of falcons begins 4-6 weeks later. Southbound semipalmated sandpipers make extended migratory stopovers, but their lengths of stay shorten prior to falcon migration to the sites in September. Predation danger also may affect the evolution of migration routes. Southbound western sandpipers fly directly from Alaska to southern British Columbia, in contrast to the multi-stage journey northward along the Alaska panhandle. We estimate that a direct flight would be more economical on northward migration, but may be avoided because it would expose sandpipers to higher mass-dependent predation danger from migratory falcons, which travel north with sandpipers. By contrast, few raptors are present in Alaska during preparation for the southward flight. A temporal and spatial window of safety may also permit semipalmated sandpipers to become extremely vulnerable while preparing for trans-Atlantic southward flights. Danger management may account for the these previously enigmatic features of calidrid migration strategies, and aspects of those of other birds.
84. Morbey, YE; Ydenberg, RC. (2003) Timing games in the reproductive phenology of female Pacific salmon (Oncorhynchus spp.).American Naturalist 161: 284-298 Timing games in the reproductive phenology of female Pacific salmon (Oncorhynchus spp.)
reproductive tactics; nest defense; longevity; reproductive phenology; salmon
We use a game-theoretic framework to investigate the reproductive phenology of female kokanee (Oncorhynchus nerka). As in the other semelparous species of Pacific salmon, females construct nests in gravel, spawn with males, bury their fertilized eggs, and defend their nest sites until they die several days later. Later-breeding females may reuse previous nest sites, and their digging behavior is thought to subject previously buried eggs to mortality. Using gametheoretic models, we show that females can reduce this risk by allocating resources to longevity (the period between arrival and death) as opposed to eggs. Waiting before territory settlement is also expected if it allows females to conserve energy and delay senescence. The models demonstrate how these costs and benefits interact to select for a seasonal decline in longevity, a well-known phenomenon in the salmonid literature, and a seasonal decline in wait duration. Both of these predictions were supported in a field study of kokanee. Female state of reproductive maturity was the most important proximate factor causing variation in longevity and wait duration. With more than 30% of territories being reused, dig-up is likely an important selective force in this population.
83. Ost, M; Ydenberg, R; Kilpi, M; Lindstrom, K. (2003) Condition and coalition formation by brood-rearing common eider females.Behavioral Ecology 14: 311-317 Condition and coalition formation by brood-rearing common eider females
body condition; brood amalgamation; coalitions; common eider; parental care; partner choice; solitary tending; Somateria mollissima
Partner choice is important in nature, and partnerships or coalitions within which reproduction is shared are the subject of growing interest. However, little attention has been given to questions of which individuals are suitable partners and why. Common eider (Somateria mollissima) females sometimes pool their broods and share brood-rearing duties, and body condition affects care decisions. We constructed a model in which females, based on their body condition and the structure of the joint brood, assess the fitness consequences of joining a coalition versus tending for young alone. We tested the model's predictions by comparing data on the condition of females in enduring and transient coalitions. Our model showed that the range of acceptable brood arrays in a female coalition decreases with increasing condition of the female, so females tending alone should be in better condition than multifemale tenders. This prediction is in agreement with previous data. The model also predicts that females in good condition should join coalitions with females in poor condition and not with other females in good condition. This prediction was also supported by data: in enduring two-female coalitions, the positive correlation between the better female's condition and the difference in condition between the two females was stronger than would be expected by random grouping of females. In contrast, in transient coalitions of females, this correlation did not differ from the correlation expected under random grouping. Model assumptions seem to fit with eider natural history, and the model may prove to be a useful way to study brood amalgamation behavior of waterfowl in general.
82. Ost, M; Ydenberg, R; Lindstrom, K; Kilpi, M. (2003) Body condition and the grouping behavior of brood-caring female common eiders (Somateria mollissima).Behavioral Ecology and Sociobiology 54: 451-457 Body condition and the grouping behavior of brood-caring female common eiders (Somateria mollissima)
body condition; ecological constraints; group size; N-person staying incentive model; Somateria mollissima
Both theoretical and empirical work has shown that group size increases with increasing ecological constraints on solitary breeding. Ecological constraints refer to extrinsic factors such as availability of breeding sites, food or mates. Common eider (Somateria mollissima) females pool their broods and share brood-rearing duties, or rear broods alone. Females are often in poor condition at hatching, as incubation is accomplished without feeding, and variation in body condition is largely environmentally induced and thus unpredictable. We found that the intensity of and duration of parental care that females provide is positively correlated with their body condition at hatching. This suggests that body condition is an ecological constraint on successful solitary breeding. We further observed that group productivity in common eider broods is a decelerating function of the number of tending females. As predicted, females in poorer condition (i.e., facing stronger ecological constraints) were found in larger groups. This result is straightforward if solitary tenders can enter any group at no cost. However, if entry is group-controlled, stable groups of non-relatives are predicted not to occur when per capita reproduction declines with group size. The N-person staying incentive model permits groups to form under these conditions, because reproduction is unevenly divided between dominants and subordinates in the group. We discuss the plausibility of these alternative models of group size for understanding the grouping behavior of brood-caring female common eiders.
81. Wardrop, SL; Ydenberg, RC. (2003) Date and parental quality effects in the seasonal decline in reproductive performance of the Tree Swallow Tachycineta bicolor: interpreting results in light of potential experimental bias.Ibis 145: 439-447 Date and parental quality effects in the seasonal decline in reproductive performance of the Tree Swallow Tachycineta bicolor: interpreting results in light of potential experimental bias
In many bird species early breeders have higher reproductive performance than late breeders from the same population. This could be caused by a reduction in environmental factors related to date per se (Date Hypothesis), or because poorer performers nest later (Parent Quality Hypothesis). We manipulated hatch date of Tree Swallows Tachycineta bicolor by switching clutches with different lay dates, generating broods with advanced or delayed timing, and assessed the impact of the experiment on nestling mass. The Date Hypothesis better explained the decline in nestling mass in the first half of the season, while the Parent Quality Hypothesis was supported in the second half. We also found that female mass loss was unintentionally reduced in advanced females and suggest that such impacts of the experiment on parent quality, or correlations between nestlings and their actual parents via heritability or maternal effects, could bias hatch-date manipulation experiments towards supporting the Date Hypothesis. Differential costs of incubation, either due to naturally low temperatures early in the season, or due to the unintentional manipulation of female incubation costs, appear to have driven support for the Date Hypothesis early in the season.
80. Burns, JG; Ydenberg, RC. (2002) The effects of wing loading and gender on the escape flights of least sandpipers (Calidris minutilla) and western sandpipers (Calidris mauri).Behavioral Ecology and Sociobiology 52: 128-136 The effects of wing loading and gender on the escape flights of least sandpipers (Calidris minutilla) and western sandpipers (Calidris mauri)
avian migration; escape; mass-dependent predation risk; take-off
High body mass caused by fat storage during migration is believed to increase a bird's risk of predation by decreasing its ability to escape predators. We demonstrate the negative effect of wing loading (mass/wing area) on escape speed and angle of two migrating species of shorebird. We also show significant differences in escape performance between the species and genders. To help explain these differences, we test two potential proximate causes, wing shape and leg bone length. Wing shape is correlated with differences in escape performance between the species, but we found no correlation of wing shape or leg bone length with gender. Ultimately, greater predation risk due to habitat use or larger body size, for the species and genders respectively, may have resulted in evolution of enhanced escape ability.
79. Hakkarainen, H; Korpimaki, E; Koivunen, V; Ydenberg, R. (2002) Survival of male Tengmalm's owls under temporally varying food conditions.Oecologia 131: 83-88 Survival of male Tengmalm's owls under temporally varying food conditions
recapture; prey abundance; three-year vole cycles; Microtus voles
We analysed whether annual survival of male Tengmalm's owls in western Finland varies according to changes in the abundance of their main prey, Microtus voles. Our analyses were based on capture-recapture data over five 3-year population cycles of voles from 1981 to 1995, each cycle consisting of consecutive years of low, increasing and decreasing vole abundance. Survival estimates of males in the increasing vole years (ca. 55%) were higher than in the decreasing vole years. In the latter case, males faced a drastic crash in Microtus vole numbers, and only about one-third of males survived over this crash. After the crash of vole populations, male survival increased rapidly (up to 76%) according to the recovery of Microtus vole populations. These results show that temporal variation in the abundance of their main prey modifies the survival of male Tengmalm's owls. In addition to survival, recapture rates also varied, largely due to the fact that in poor vole years a majority of-males skipped breeding. The large among-cycle phase variation in survival (25-76%) probably creates selection for phenotypic plasticity in life-history traits related to survival and reproduction.
78. Hakkarainen, H; Yli-Tuomi, I; Korpimaki, E; Ydenberg, R. (2002) Provisioning response to manipulation of apparent predation danger by parental Pied Flycatchers.Ornis Fennica 79: 139-144 Provisioning response to manipulation of apparent predation danger by parental Pied Flycatchers
We tested whether nest visitation rate of parent Pied Flycatchers (Ficedula hypoleuca) is decreased by an experimentally increased predation risk. We simulated predation risk by placing a stuffed Pygmy Owl (Glaucidium passerinum) in the nest vicinity and by playback of pygmy owl's whistling. We used Blackbird (Turdus merula) treatment as a control. Surprisingly, the parental nest visitation rate was about 25% higher in the treatment than in the control group. The treatments were reversed on the same day. Pairs of the "control treatment" in the first phase increased their nest visitation rate by 16% as a response to the "owl treatment". Four possible explanations exist. Parents may increase delivery in order (1) to silence the begging of the nestlings, who might otherwise betray the nest location to the owl, or (2) to increase the growth rate of the nestlings so that they fledge sooner, probably disperse better and so elude the danger. Alternatively, (3) the parents may view a predator as a threat to themselves, and remain in the vicinity of the nest where they are most familiar and therefore safest. In addition, (4) increased nest visitation might form part of nest defense behaviour against the owl.
77. Hazlitt, SL; Ydenberg, RC; Lank, DB. (2002) Territory structure, parental provisioning, and chick growth in the American Black Oystercatcher Haematopus bachmani.Ardea 90: 219-227 Territory structure, parental provisioning, and chick growth in the American Black Oystercatcher Haematopus bachmani
Haematopus bachmani; American Black Oystercatchers; provisioning rates; chick growth; territory structure
We investigate parental food provisioning and chick growth to better understand how parental effort and territory structure relate to reproductive success in the American Black Oystercatcher. American Black Oystercatcher chick diet was comprised mainly of limpets. Most prey items were 20 mm or shorter in length. Provisioning rates (kJ h(-1)) were significantly correlated with mean delivery rates rather than mean prey size, and higher provisioning rates resulted from a greater number of deliveries of small prey items. Provisioning rates were extremely variable among pairs but increased significantly with brood size and brood age. Larger brood sizes occurred more frequently on shallow sloped territories, therefore provisioning rates were significantly higher on shallow sloped than steep sloped territories. Provisioning rates appeared to decrease with increasing intertidal slope, a trend significantly supported by the growth patterns of the slow-growing chick in multi-chick broods. The effect of intertidal slope became more important when chicks were older and demand was higher, with parents occupying shallow territories achieving higher provisioning rates to older chicks relative to parents on steep territories. We discuss the hypothesis that American Black Oystercatcher parents adjust parental effort with respect to territory quality and propose possible parental adjustment mechanisms.
76. Lozano, GA; Ydenberg, RC. (2002) Transgenerational effects of maternal immune challenge in tree swallows (Tachycineta bicolor).Canadian Journal of Zoology-Revue Canadienne de Zoologie 80: 918-925 Transgenerational effects of maternal immune challenge in tree swallows (Tachycineta bicolor)
The fact that avian eggs contain antibody of maternal origin is well documented, but only recently has this phenomenon been considered in an ecological context. We used tree swallows (Tachycineta bicolor) to examine the possibility of transgenerational immunity and its effect on nestling growth and immune development. We measured cell-mediated immunity with a delayed-hypersensitivity assay and antibody-mediated immunity with a hemagglutination test with sheep red blood cells (SRBCs). We tested for differences in immunocompetence and growth between nestlings from females who had been exposed to a novel antigen prior to egg laying and nestlings from unexposed females. To determine whether the effect, if any, resulted from something transferred to the eggs prior to egg laying or from subsequent changes in parental behaviour, nestlings were exchanged so that at each nest half the nestlings were from females who had been injected with SRBCs and half were from females who had not been exposed to SRBCs. Finally, brood sizes were independently manipulated to either 4 or 6 nestlings. We failed to detect maternal antibodies in any nestlings, and whether a female was exposed to SRBCs or not had no effect on the growth or cell-mediated immunity of her brood. However, nestlings in smaller broods grew better than nestlings in larger broods, though we did not find the expected differences in cell-mediated immunity. Furthermore, within each nest, nestlings whose mothers had been exposed to SRBCs grew better than nestlings whose mothers had not been exposed. These results are contrary to the idea of a simple trade-off in the allocation of resources between parasite protection and reproduction; however, they support the idea that exposure of females to parasites prior to egg laying leads to better nestling growth, and are congruous with the possibility of mithridatic parental care.
75.Ydenberg, RC; Butler, RW; Lank, DB; Guglielmo, CG; Lemon, M; Wolf, N. (2002) Trade-offs, condition dependence and stopover site selection by migrating sandpipers.Journal of Avian Biology 33: 47-55 Trade-offs, condition dependence and stopover site selection by migrating sandpipers
Western sandpipers Calidris mauri on southward migration fly over the Gulf of Alaska to the Strait of Georgia, British Columbia, where they stop for a few days to replenish reserves before continuing. In the Strait, individuals captured on the extensive tidal mudflats of the Fraser estuary (similar to 25000 ha) are significantly heavier (2.71 g, or > 10% of lean body mass) than those captured on the small (< 100 ha) mudflat of nearby Sidney Island. Previous work has shown that the difference cannot be attributed to seasonal timing, size, age or gender effects, and here we compare predictions made by six hypotheses about a diverse set of data to explain why, partway through a migratory journey of similar to 10 000 km, birds have such different body masses at two stopover sites within 40 km of each other. The 'trade-off' hypothesis - that the large Fraser estuary offers safety from predators, but a lower fattening rate, while the small Sidney Island site is more dangerous, but offers a higher fattening rate - made six successful predictions, all of which were upheld by the data. All other hypotheses failed at least one prediction. We infer that calidrid sandpipers arriving in the Strait of Georgia with little fat remaining (and therefore low body mass) choose to take advantage of the high feeding rate at small sites like Sidney Island because they are less vulnerable to avian predators than are individuals with higher fat reserves, who instead elect to feed at large open sites like the Fraser estuary mudflats.
74. Burness, GP; Ydenberg, RC; Hochachka, PW. (2001) Physiological and biochemical correlates of brood size and energy expenditure in tree swallows.Journal of Experimental Biology 204: 1491-1501 Physiological and biochemical correlates of brood size and energy expenditure in tree swallows
energetics; doubly labelled water; daily energy expenditure; parental care; clutch size; fitness; performance; provisioning; enzyme activity; tree swallow; Tachycineta bicolor
Intra-population variation in many fitness-related traits (e,g, clutch size) is often attributed to variation in individual parental quality. One possible component of quality is the level at which each individual can expend energy while provisioning dependent young, We used breeding tree swallows (Tachycincta bicolor) to test whether adults with large, natural-sized broods and/or nestlings in good nutritional condition had relatively high daily energy expenditures (DEEs). Adults with high DEEs were predicted to have large internal organs and high metabolic capacities, We first measured the growth rate of nestlings in natural broods of five, six and seven over a 4-day period and then measured parental DEE using doubly labelled water. Adults mere then dissected for analyses of body composition and to determine maximum enzyme activities in the pectoral muscle. Although the total mass gain of large broods was greater than that of small broods, parental DEE was independent of brood size. We hypothesize that adults matched their clutch size (and consequently, brood size) to their individual foraging efficiencies. When statistically controlling for the effects of brood size, in one of two years there was a positive correlation between DEE and brood mass. This suggests that among individuals rearing the same-sized broods there were reproductive benefits of a relatively high DEE, There was no correlation between either brood size or DEE and the mass of any internal organ or the metabolic capacity of the pectoral muscle.
73. Morbey, YE; Ydenberg, RC. (2001) Protandrous arrival timing to breeding areas: a review.Ecology Letters 4: 663-673 Protandrous arrival timing to breeding areas: a review
arrival timing; behavioural ecology; breeding schedule; emergence; migration; protandry; protogyny
Protandry, the earlier arrival of males to breeding areas than females, is a common pattern of sex-biased timing in many animal taxa (e.g. some insects, fish, amphibians, reptiles, birds and mammals). The adaptive significance of protandry is not fully understood and, since the 1970s, at least seven hypotheses for protandry have been proposed. We describe each of these hypotheses and summarize what is known about each. In three of these hypotheses, the relative arrival timing of males and females has no direct fitness consequences for males or females, but selection for different timing in each sex indirectly produces protandry. In the other four hypotheses, the difference between male and female timing has fitness consequences for males or females and selection directly maintains the fitness-maximizing degree of sex-biased timing. The hypotheses are not mutually exclusive, and the degree of multiple mating by males and the occurrence of male territoriality seem to determine the relative importance of each hypothesis. In order to understand the adaptive significance of sex-biased timing, future studies need to consider all the alternatives and to assess the costs and benefits to males of early arrival relative to calendar date, to other males and to females.
72.Ydenberg, RC. (2001) Precocial nest departure in the Alcidae.Evolutionary Ecology Research 3: 179-190 Precocial nest departure in the Alcidae
alcid nest departure; Ancient Murrelet; growth-mortality trade-off; parent-offspring conflict; precocity
The avian family Alcidae is unique among birds in having species with widely divergent developmental modes. In all alcids, the juvenile phase is composed of a period spent in the nest and a subsequent period at sea completing growth; the age at transition varies greatly between species Previously, semi-precocial (species completing more than half of growth in the nest before departure to the sea) and intermediate (one-quarter to one-third of growth) alcid species have been modelled. Here a model is developed to investigate selective factors favouring the evolution of precocial nest departure in the Ancient Murrelet Synthliboramphus antiquus. The fitness-maximizing age to make the transition from nest to sea (nest departure) is calculated under various assumptions, for both parents and offspring. The model shows that the potential for growth at sea following nest departure is the strongest factor influencing the age at departure. A second important factor is the danger posed by predators to provisioning parents while the two-egg clutch of murrelets (most other alcids lay a single egg) is less important. There is a small region of the parameter space (with high ocean growth and dangerous provisioning) within which precocial nest departure is favoured from the point of view of both parents and offspring. The zone of conflict between parents and offspring is also narrow. These results are evaluated with respect to the precocity hypothesis of Gaston.
69. Janmaat, AF; Winston, ML; Ydenberg, RC. (2000) Condition-dependent response to changes in pollen stores by honey bee (Apis mellifera) colonies with different parasitic loads.Behavioral Ecology and Sociobiology 47: 171-179 Condition-dependent response to changes in pollen stores by honey bee (Apis mellifera) colonies with different parasitic loads
honey bee; Varroa jacobsoni; pollen foraging; parasitism; efficiency
The impact of a parasitic infestation may be influenced by nutritional state, in both individuals and colonies. This study examined the interaction between pollen storage and the effects of an infestation by the mite, Varroa jacobsoni Oudemans, in colonies of the honey bee, Apis mellifera L. We manipulated the pollen storage and mite infestation levels of colonies, and measured pollen foraging and brood rearing. Increased pollen stores decreased both the number of pollen foragers and pollen load size, while initially at least foragers from colonies with moderate infestations carried smaller pollen loads than those from lightly infested colonies. Over the course of the experiment, all colonies significantly increased pollen-foraging rates and pollen consumption, which was presumably a seasonal effect. Lightly infested colonies exhibited a larger increase in pollen forager number than moderately infested colonies, suggesting that more intense mite infestations compromised forager recruitment. Brood production was not affected by the addition of pollen, but moderately infested colonies were rearing significantly less brood by the end of the experiment than lightly infested colonies. Furthermore, the efficiency with which colonies converted pollen to brood decreased as the pollen storage level decreased and the infestation level increased. The results of this study may indicate that honey bee colonies adaptively alter brood-production efficiency in response to parasitic infestations and seasonal changes.
67. Morbey, YE; Ydenberg, RC; Knechtel, HA; Harfenist, A. (1999) Parental provisioning, nestling departure decisions and prefledging mass recession in Cassin's auklets.Animal Behaviour 57: 873-881 Parental provisioning, nestling departure decisions and prefledging mass recession in Cassin's auklets
We investigated how parental provisioning and nestling departure behaviour interact to produce prefledging mass recession in Cassin's auklets, Ptychoramphus aleuticus. Under our hypothesis, auklet parents are reluctant provisioners and should be increasingly likely to terminate or reduce provisioning of their single nestling as it matures. For the nestling, remaining in the nest presents a risk of losing mass (if the parent does not provision) but also a possibility of additional provisioning. As the nestling matures and becomes increasingly capable of independence, the benefits of remaining in the nest decrease and nestlings should be increasingly likely to fledge. Nestlings also should be more likely to fledge when the expectation of additional provisioning is low. Data on parental provisioning (based on growth increments) and nestling departure were consistent with our hypothesis. Older and heavier nestlings had smaller growth increments than younger and lighter nestlings, suggesting that parents were reluctant to provision old and heavy nestlings. Older and heavier nestlings also were increasingly likely to fledge. We hypothesized that nestlings might use the intensity of mass loss to gauge parental reluctance to provision, and accordingly, nestlings were increasingly likely to fledge after experiencing a greater amount of mass loss. (C) 1999 The Association for the Study of Animal Behaviour.
66. Smith, TE; Ydenberg, RC; Elner, RW. (1999) Foraging behaviour of an excavating predator, the red rock crab (Cancer productus Randall) on soft-shell clam (Mya arenaria L.).Journal of Experimental Marine Biology and Ecology 238: 185-197 Foraging behaviour of an excavating predator, the red rock crab (Cancer productus Randall) on soft-shell clam (Mya arenaria L.)
burial depth; handling time; prey profitability; Cancer productus; Mya arenaria
We investigated the influence of soft-shell clam (Mya arenaria) burial depth on red rock crab (Cancer productus) foraging behaviour. In laboratory tanks, crabs searched for and excavated clams buried at depths of 5, 10, and 15 cm. Handling time of prey was partitioned into excavation time, breaking time, and eating time. Prey excavation formed 23% of mean total handling time (mean 8.2 min total 35.7 min(-1)) at 5 cm prey depth, 62% at 10 cm depth (mean 49.3 min total 79.5 min(-1)), and 73% at 15 cm depth (mean 93.5 min total 128.2 min(-1)). Mean excavation time for clams increased at a rate of 8.3 min cm(-1) of depth; clam profitability (energy intake per unit handling time (J s(-1))) decreased with burial depth. Predation rates decreased with prey burial depth. Often crabs gave up attempts to excavate a clam, and abandonment frequency and excavation time before abandonment increased significantly (p < 0.05) with burial depth. Our findings confirm earlier studies which indicate that burial depth affords an important refuge from crab predation, significantly increasing prey handling time and decreasing the profitability of individual prey. (C) 1999 Elsevier Science B.V. All rights reserved.
65. Burness, GP; Ydenberg, RC; Hochachka, PW. (1998) Interindividual variability in body composition and resting oxygen consumption rate in breeding tree swallows, Tachycineta bicolor.Physiological Zoology 71: 247-256 Interindividual variability in body composition and resting oxygen consumption rate in breeding tree swallows, Tachycineta bicolor
Basal metabolic rate is one of the most widely measured physiological traits. Previous studies on lab mice and field-caught lizards suggest that individuals with relatively high basal metabolic rates or standard metabolic rates have relatively large masses of metabolically active tissues (e.g., heart, kidney, liver). As these are energetically expensive organs, there may be variability between breeding seasons dependent on, for example, availability of prey and capacity for energy intake. We present data from breeding tree swallows (Tachycineta bicolor) collected over two successive seasons. There was no difference between years in resting oxygen consumption rates, although there were significant interannual differences in the masses of all organs and tissues except the pectoralis. Interindividual differences in the masses of the kidney and small intestine explained 21% of the variation in oxygen consumption rates. Although individuals with relatively high resting oxygen consumption rates had relatively large, metabolically active kidneys, they had relatively small intestines and pectoral muscles. This is in contrast to all previous studies on mammals and to the single interspecific study of birds. Oxygen consumption rate also correlated positively with hematocrit. Our results suggest that assumptions of consistent positive relationships between resting oxygen consumption rate and organ masses cannot be extended intraspecifically for birds.
64. Machmer, MM; Ydenberg, RC. (1998) The relative roles of hunger and size asymmetry in sibling aggression between nestling ospreys, Pandion haliaetus.Canadian Journal of Zoology-Revue Canadienne de Zoologie 76: 181-186 The relative roles of hunger and size asymmetry in sibling aggression between nestling ospreys, Pandion haliaetus
The food-amount hypothesis, proposed to account for sibling aggression in brood-reducing bird species, predicts that broods will be aggressive when hungry, and that as a result, senior siblings will be able to take a greater share of the total available food. We performed a field experiment to test these predictions in ospreys, Pandion haliaetus. Broods were removed from their natal nests and subjected to a series of experimental trials. Each trial consisted of a 3.5-h starvation period followed by a feeding or sham-feeding treatment designed to manipulate the hunger of the nestlings. Following treatment, broods were placed in a viewing nest along with a fish. While the viewing-nest mother fed the fish to the brood, we recorded food allocation and aggresssion. Each of 10 broods experienced a number (one to six) of feeding and sham-feeding treatments over a period of 2 days and was then returned to its natal nest. Broods were slightly but significantly more aggressive after sham-feeding treatments, and senior siblings took a greater share of the meal. The tremendous variation in the level of sibling aggression observed between broods was inversely related to brood mass asymmetry but not to condition, suggesting that siblings adjusted the rate of aggression according to the level of competition within their broods.
63.Ydenberg, R; Hurd, P. (1998) Simple models of feeding with time and energy constraints.Behavioral Ecology 9: 49-53 Simple models of feeding with time and energy constraints
efficiency maximization; foraging theory rate maximization; submaximal foraging; workload
We analyze how the foraging currencies "rate" (net energy gain per unit time) and "efficiency" (net energy gain per unit energy expenditure) relate to the workload adopted by a forager. We consider feeding (gathering food for immediate consumption) as opposed to provisioning and investigate the influence of time and energy constraints. In our model the forager may vary the level of energy expenditure while foraging; increased expenditure increases the rate of gain, but with diminishing returns. We show that rate maximizing requires a higher rate of energy expenditure than efficiency-maximizing, and we compare the performance of rate-and efficiency-maximizing tactics when the feeding strategy is (1) to maximize the total net gain while foraging; (2) to maximize the total net daily gain; or (3) to meet a requirement. Generally, the rate-maximizing tactic only performs best when time is limiting; other wise, a lighter workload and slower feeding rate perform better. Under the restricted conditions analyzed here, no general statement can be made about the best tactic when the strategy is to meet a requirement. These results may help explain several instances of "submaximal" foraging described in the literature.
61. Houtman, R; Paul, LR; Ungemach, RV; Ydenberg, RC. (1997) Feeding and predator-avoidance by the rose anemone Urticina piscivora.Marine Biology 128: 225-229 Feeding and predator-avoidance by the rose anemone Urticina piscivora
We investigated the influence of feeding rate on the behavior of the rose anemone Urticina piscivora. We predicted that anemones would travel less and be less willing to detach from the substrate in response to contact with a predator (Dermasterias imbricata) as feeding rate was experimentally increased. As predicted, anemones receiving 0 mussels (Mytilus trossulus) daily moved significantly more than those receiving either 1 or 2 mussels daily. Anemones receiving 0 mussels daily also detached significantly quicker in response to predator contact compared to the I mussel per day group, which in turn detached significantly quicker than did the 2 mussels per day group. A field test of the same prediction gave mixed results. We also examined whether anemones could detect feeding rates of neighbors. Movement rates of anemones receiving 1 mussel daily when neighbors received 0 mussels daily were compared with those when neighbors received 2 mussels daily. We predicted that if the subjects could detect feeding rates of neighbors, they should move less when neighbors received less food than themselves (since their position is relatively good) than when neighbors received more food. The results support this interpretation.
60. Morbey, YE; Ydenberg, RC. (1997) Intraspecific variability in nestling growth and fledging behavior of Cassin's Auklets at Triangle Island, British Columbia.Condor 99: 361-371 Intraspecific variability in nestling growth and fledging behavior of Cassin's Auklets at Triangle Island, British Columbia
fledging; nestling growth; Cassin's Auklet; Triangle Island
We compared nestling growth and fledging behavior of Cassin's Auklets (Ptychoramphus aleuticus) at Triangle Island, British Columbia to the predictions of a model that considers the timing of fledging to be an adaptive strategy. In the model, hedging mass and age depend on nestling growth rate, time remaining in the season, and the contrasting mortality costs and growth benefits experienced before and after fledging. As predicted, fast growing nestlings hedged heavier and younger than slow growing nestlings. Growth rates declined over the season and hedging behavior varied accordingly. When the seasonal variation in growth rates was statistically controlled, late nestlings did not fledge lighter and younger, in contrast to the model's predictions. Late in the season, nestlings reached a greater peak mass than expected based on their slower growth rates. Also, nestlings that grew more slowly due to a higher frequency of handling reached a higher peak mass than less frequently measured nestlings. We consider the possibility that parents adaptively modified their nestling's growth trajectory by altering provisioning behavior in response to nestling condition. The nesting habitat influenced fledging. Fast growing nestlings fledged at similar ages in both level and steep nest sites. In contrast, slow growing nestlings fledged at younger ages, but similar masses, in level sites compared to steep sites. We consider the possibility that the difference in parental predation risk between level and steep nest sites influenced provisioning decisions of parents, and consequently, hedging decisions of nestlings.
59. Zaklan, SD; Ydenberg, R. (1997) The body size burial depth relationship in the infaunal clam Mya arenaria.Journal of Experimental Marine Biology and Ecology 215: 1-17 The body size burial depth relationship in the infaunal clam Mya arenaria
beach elevation; burial depth; Cancer productus; filtration rate; infaunal; Mya arenaria; model; predator-prey; predator avoidance behaviour; trade-off
Larger infaunal organisms tend to be buried more deeply than smaller conspecifics, but the ultimate (natural selection) reasons for this have received little attention. A model to explain this ubiquitous pattern is based on several key assumptions: (1) deeper burial increases survival, but (2) slows the feeding rate, and (3) large individuals are able to feed mon rapidly than small individuals at any depth, Under these assumptions, the fitness-maximizing burial depth for a large individual is greater than for a small individual. Larger individual soft-shell clams Mya arenaria (Linnaeus) were buried more deeply than smaller conspecifics on each of five beaches. Field observations and experiments confirmed that shallowly buried individuals had a lower survival rate than those buried more deeply, due to predation by the red rock crab Cancer productus (Randall). Laboratory measurements of the clearance rates of experimentally buried clams confirmed assumptions (2) and (3). Field measurements of the survival of marked and experimentally buried clams showed that clams were at greater risk of excavation by red rock crabs at low than at high beach elevations, and showed that crab excavation activity decreased with beach elevation. Thus, the risk of mortality for soft-shell clams is higher at low beach elevations. As the model predicts, the burial depth-body size relationship is shifted downwards at low beach elevations. Laboratory experiments discounted the possibility that substratum differences could account for this difference, and furthermore showed that clam burial behavior could be altered by treatments intended to simulate cues about crab activity. We conclude that the positive relation between size and burial depth observed in Mya arenaria arises from trade offs between feeding opportunity and mortality risk. (C) 1997 Elsevier Science B.V.
58. Bertram, DF; Welham, CVJ; Ydenberg, RC. (1996) Flexible effort in breeding seabirds: Adjustment of provisioning according to nestling age and mass.Can. J. Zool.-Rev. Can. Zool. 74: 1876-1881 Flexible effort in breeding seabirds: Adjustment of provisioning according to nestling age and mass
We examined whether rhinoceros auklet (Cerorhinca monocarata) parents are able to adjust their provisioning effort in response to chick demand. A fostering experiment in which nestlings of different ages and masses were exchanged between burrows was employed to examine parental provisioning effort before and after the exchange. Daily mass increments of the nestlings were used to estimate the amount fed on the previous night, using a model based on data from captive chicks raised on a controlled diet. Our results demonstrate that rhinoceros auklet parents somehow assess and respond to the needs of their chicks by delivering more to order and larger fostered chicks and less to younger and smaller fostered chicks. Our results confirm and extend a growing body of information which shows that seabird parents can adjust provisioning effort when feeding young. We highlight how studies to date have differentially manipulated nestling age and hunger, thus complicating a comparative approach. Testing for interspecific differences in parental ability to respond to chick demands will require studies that employ comparable types of manipulations for a variety of seabird species. DOI
57. Hurd, PL; Ydenberg, RC. (1996) Calculating the ESS level of information transfer in aggressive communication.Evolutionary Ecology 10: 221-232 Calculating the ESS level of information transfer in aggressive communication
communication; threat; cost; honesty; aggression
We present a model of aggressive communication that demonstrates the use of evolutionarily stable ambiguous threat displays. We use stochastic dynamic programming to solve a game in which two contestants of differing fighting ability communicate using cost-free threats. These contestants use communication strategies that supply information of varying reliability to the opponent. The results demonstrate that communication does not need to be either costly or unambiguous to be evolutionarily stable.
56. Price, K; Harvey, H; Ydenberg, R. (1996) Begging tactics of nestling yellow-headed blackbirds, Xanthocephalus xanthocephalus, in relation to need.Animal Behaviour 51: 421-435 Begging tactics of nestling yellow-headed blackbirds, Xanthocephalus xanthocephalus, in relation to need
Theoretical models suggest that begging may signal nestling need. 'Need' for food can be either short term (hunger) or long term (amount of food required to hedge, which may be influenced by body condition, sex or rank in the brood). Studies have shown that begging carries information about short-term need, but have not provided evidence that begging can carry information about long-term need. Signals of long-term need may be unstable if larger chicks out-compete their needler siblings. This study investigated whether nestling yellow-headed blackbirds beg according to long-term need in field and laboratory experiments. In yellow-headed blackbirds, smaller nestlings, males and chicks in poor condition should value food more highly. When hunger level was controlled, males and chicks in poor condition begged more than females and chicks in good condition, respectively, and chicks begged more when paired with larger rather than smaller nestmates. In yellow-headed blackbirds, even when nestmates have unequal competitive abilities, begging can carry information about nestling long-term need for food. (C) 1996 The Association for the Study of Animal Behaviour
55. Waite, TA; Ydenberg, RC. (1996) Foraging currencies and the load-size decision of scatter-hoarding grey jays.Animal Behaviour 51: 903-916 Foraging currencies and the load-size decision of scatter-hoarding grey jays
Food-hoarding animals are assumed to maximize total storage while meeting their own energetic requirements. To maintain energetic balance, a hoarder must also devote some time to feeding. The predicted choice of hoarding strategy depends on the net rate at which a hoarder is able to feed itself. Rate-maximizing hoarding is favoured when the net self-feeding rate is high, as it was during our experiment. (At lower net self-feeding rates, the hoarder should behave more efficiently.) To evaluate the expectation of rate maximization, we examined load-size decisions (number of raisins collected for storage) made by hoarding grey jays, Perisoreus canadensis. During each visit to an experimental food source, the subject was forced to wait for access to the food. Following this delay, the jay collected a load, transported it for storage, and returned to the source. The predicted size of rate- and efficiency-maximizing loads diverged with increases in the delay. As predicted by both currencies, the jays collected larger loads following longer delays. The magnitude of the observed adjustments indicates that the jays closely approached the maximal rate of hoarding. (C) 1996 The Association for the Study of Animal Behaviour
54. HARFENIST, A; YDENBERG, RC. (1995) PARENTAL PROVISIONING AND PREDATION RISK IN RHINOCEROS AUKLETS (CERORHINCA-MONOCERATA) - EFFECTS ON NESTLING GROWTH AND FLEDGING.Behav. Ecol. 6: 82-86 PARENTAL PROVISIONING AND PREDATION RISK IN RHINOCEROS AUKLETS (CERORHINCA-MONOCERATA) - EFFECTS ON NESTLING GROWTH AND FLEDGING
FLEDGING; GROWTH; PARENTAL PROVISIONING; PREDATION RISK; RHINOCEROS AUKLET
We examined the effects of predation risk on the behavior of rhinoceros auklets (Cerorhinca monocerata) breeding at Pine Island, British Columbia, in 1990. Provisioning parents in some areas of the colony risked predation by bald eagles (Haliaeetus leucocephalus). Chicks in high and low predation risk areas of the colony hatched on approximately the same date, received similar amounts of food to 46 days of age, grew at the same rate, reached similar peak masses, and fledged at similar masses. However, chicks in high predation areas fledged at a younger age than did chicks in low predation areas. These data are consistent with the hypothesis that parents in high risk areas terminated provisioning several days before those in lower risk areas. Mass at fledging was inversely related to age at fledging in both high and low risk areas. The regression line for the high risk habitats lies below that from the low risk habitats, as predicted by a model that examines optimal time of fledging from the perspective of the parents. We conclude that risk of predation represents a significant cost of reproduction to some rhinoceros auklets and that individual auklets within the colony vary their behavior according to predation risk. DOI
53. PRICE, K; YDENBERG, R. (1995) BEGGING AND PROVISIONING IN BROODS OF ASYNCHRONOUSLY-HATCHED YELLOW-HEADED BLACKBIRD NESTLINGS.Behav. Ecol. Sociobiol. 37: 201-208 BEGGING AND PROVISIONING IN BROODS OF ASYNCHRONOUSLY-HATCHED YELLOW-HEADED BLACKBIRD NESTLINGS
YELLOW-HEADED BLACKBIRDS; BEGGING; PROVISIONING; ASYNCHRONOUS HATCHING; SIBLING COMPETITION
Studies of begging have found a positive relationship between begging level and provisioning level. Studies of unequal nestlings, however, have found that small nestlings generally beg more but are fed less than their larger siblings. We manipulated the begging levels of yellow-headed blackbird (Xanthocephalus xanthocephalus) chicks to investigate how begging benefits individuals in broods of unequal siblings. Food-deprived chicks begged more and were fed more; satiated chicks begged less and were fed less. When we deprived each chick of a brood in turn, large and small chicks generally increased begging and received more provisioning. Small chicks, however, rarely received more food than their larger siblings even when they begged relatively more. Parent yellow-headed blackbirds increase provisioning to hungry begging chicks, but also allocate food based on relative offspring size. DOI
51. YDENBERG, RC; CLARK, CW; HARFENIST, A. (1995) INTRASPECIFIC FLEDGING MASS VARIATION IN THE ALCIDAE, WITH SPECIAL REFERENCE TO THE SEASONAL FLEDGING MASS DECLINE.Am. Nat. 145: 412-433 INTRASPECIFIC FLEDGING MASS VARIATION IN THE ALCIDAE, WITH SPECIAL REFERENCE TO THE SEASONAL FLEDGING MASS DECLINE
Species in the avian family Alcidae show enormous inter- and intraspecific variation in age and mass at nest departure (hedging). We develop a dynamic programming model of the nest departure decision that incorporates the differential growth benefits and mortality costs of the pre- and postfledging habitats (nest and ocean). The model's most basic prediction is the existence of a negatively inclined fledging boundary in mass-time space: nestlings fledge as their growth trajectory hits the boundary. The consequence is that faster-growing nestlings fledge younger and heavier than slower growers and that later-hatched nestlings fledge younger and lighter. A review of the comparative and experimental data in the literature largely supports these predictions. We use the model to show how a widespread pattern reported in the literature-the seasonal hedging mass decline-arises because of the interaction of growth and hatching date variation with the fledging strategy modeled here. The seasonal decline occurs in the absence of any of the causes most commonly suggested in the literature, particularly the seasonal decline in food availability. A detailed case study of the rhinoceros auklet (Cerorhinca monocerata) strongly supports the mechanism outlined here. DOI
50. ECKERT, CD; WINSTON, ML; YDENBERG, RC. (1994) THE RELATIONSHIP BETWEEN POPULATION-SIZE, AMOUNT OF BROOD, AND INDIVIDUAL FORAGING BEHAVIOR IN THE HONEY-BEE, APIS-MELLIFERA L.Oecologia 97: 248-255 THE RELATIONSHIP BETWEEN POPULATION-SIZE, AMOUNT OF BROOD, AND INDIVIDUAL FORAGING BEHAVIOR IN THE HONEY-BEE, APIS-MELLIFERA L
HONEY BEE; FORAGING BEHAVIOR; COLONY STATE
This study experimentally examines the relationship between colony state and the behaviour of individual pollen and nectar foragers in the honey bee, Apis mellifera L. In the first experiment we test the prediction that individual pollen foragers from colonies with higher brood quantities should exhibit a greater work effort for pollen resources than individual pollen foragers from colonies with low brood quantities. Eight colonies were assigned into two treatment groups; HIGH brood colonies were manipulated to contain 9600+/-480 cm2 brood area; LOW brood colonies were manipulated to contain 1600+/-80 cm2 brood area. We measured colony brood levels over the course of the experiment and collected individual pollen loads from returning pollen foragers. We found that, while colonies remained significantly different in brood levels, individual pollen foragers from HIGH brood colonies collected larger loads than individuals from LOW brood colonies. In the second experiment we investigated the influence of colony size on the behaviour of individual nectar foragers. We assigned eight colonies to two treatment groups; LARGE colonies were manipulated to contain 35000+/-1700 adult workers with 3500+/-175 cm2 brood area, and SMALL colonies were manipulated to contain 10000+/-500 adult workers with 1000+/-50 cm2 brood area. We observed foraging trips of individually marked workers and found that individuals from LARGE colonies made longer foraging trips than those from SMALL colonies (LARGE: 1666.7+/-126.4 seconds, SMALL: 1210.8+/-157.6 seconds), and collected larger nectar loads (LARGE: 19.2+/-1.0 mul, SMALL: 14.6+/-0.8 mul). These results indicate that individual nectar foragers from LARGE colonies tend to work harder than individuals from SMALL colonies. Both experiments indicate that the values of nectar and pollen resources to a colony change depend on colony state, and that individual foragers modify their behaviour accordingly. DOI PubMed
49. GREEN, DJ; YDENBERG, RC. (1994) ENERGETIC EXPENDITURE OF MALE OSPREYS PROVISIONING NATURAL AND MANIPULATED BROODS.Ardea 82: 249-262 ENERGETIC EXPENDITURE OF MALE OSPREYS PROVISIONING NATURAL AND MANIPULATED BROODS
This study examined the relationship between brood size and energetic expenditure of male Ospreys. The daily energetic expenditure (DEE) of male Ospreys, provisioning nestlings and providing post-fledging parental care, was estimated using detailed time-energy budgets. Factors affecting DEE were investigated, and DEE and the maximum rate of energy assimilation were compared to determine whether physiological constraints limit energetic expenditure. The DEE of male Ospreys was independent of brood age, but increased linearly with brood size. Males provisioning three-chick broods had a mean DEE of 1336 kJ/day, significantly more than the mean of 1084 kJ/day expended by males provisioning single-chick broods. Male Ospreys, however, did not respond to brood size manipulations by altering their energetic expenditure, indicating that male DEE is not directly determined by brood size. Male Ospreys also did not alter their intake rates when provisioning enlarged broods and the mean brood growth rate following brood enlargement was consequently reduced. Weather conditions had a small affect on DEE; male Ospreys had a lower energetic expenditure on days when the water surface was calm for a longer time. The DEE of male Ospreys in this study was estimated to be well below the maximum they are able to sustain. Physiological constraints therefore appear unlikely to limit brood size in Ospreys. It is suggested that individual differences in age or current condition may influence both brood size and the level of energetic expenditure of male Ospreys as these factors could affect an individual's residual reproductive value and the magnitude of the costs associated with various levels of reproductive effort.
47. WAITE, TA; YDENBERG, RC. (1994) WHAT CURRENCY DO SCATTER-HOARDING GRAY JAYS MAXIMIZE.Behav. Ecol. Sociobiol. 34: 43-49 WHAT CURRENCY DO SCATTER-HOARDING GRAY JAYS MAXIMIZE
FORAGING THEORY; GRAY JAYS; HOARDING; RATE MAXIMIZATION
Gray jays (Perisoreus canadensis) cache thousands of food items during each summer for use during the subsequent winter. Previous work on the economics of gray jay scatter-hoarding behavior was based on the assumption that the jays maximize the rate at which they store food energy; alternative currencies were not considered. Here we develop and test models based on two currencies, net rate (net recoverable energy stored per unit time) and efficiency (recoverable energy stored per unit energy expended). Our experiment involved providing gray jays with two options. After collecting a single food item upon arrival at a feeding apparatus, a jay could wait for two additional food items to become (simultaneously) available and then transport all three items for storage in scattered arboreal sites. Alternatively, the jay could immediately transport the single item to a storage site and return to the source repeatedly for additional single-item loads. By incrementally increasing the amount of time jays were required to wait for multiple-item loads, we were able to determine how long jays would wait before switching from multiple- to single-item caching trips. In contrast with the finding in a variety of species that efficiency-maximization models provide a better account of foraging behavior, the net rate-maximization model was a better predictor of the jays' switching point than was the efficiency-maximization model (Figs. 2 and 3). We discuss these conflicting results in the context of recent theory that describes the conditions favoring rate- versus efficiency-maximizing behavior (Ydenberg et al. 1994).
46. YDENBERG, R; SCHMIDHEMPEL, P. (1994) MODELING SOCIAL INSECT FORAGING.Trends Ecol. Evol. 9: 491-493 MODELING SOCIAL INSECT FORAGING
Foraging in the social insects can be viewed as a provisioning process, in which workers are powered by one resource (e.g. nectar) to deliver another (e.g. pollen) for the colony. The rate of delivery of a resource depends on the number of workers and how hard they work, which may depend on self-feeding rate. Whether individuals sacrifice their own foraging efficiency in favour of colony performance is unclear, as theory and experiment have not yet properly addressed these issues. DOI PubMed
45.Ydenberg, RC. (1994) The behavioral ecology of provisioning in birds.Ecoscience 1: 1-14 The behavioral ecology of provisioning in birds
central place foraging theory; delivery; self-feeding; provisioning; risk sensitivity; predation danger; workload
In this review, I outline the idea of provisioning, stressing the difference between self-feeding and delivery. Foraging studies have just begun to recognize this distinction, and to explore some of its implications for behavior. I outline a basic model of provisioning, based on central place foraging, in which the forager must spend some extra time on each excursion to gather enough energy to cover the excursion's energetic costs. I describe studies of provisioning pertinent to this framework, consider risk-sensitive provisioning, and use the ideas to develop a model that explores the previously-unasked question of when provisioners should deliver whole prey, and when they should deliver processed prey (e.g. the stomach oil of some procellariforms). I also discuss the role of predation danger in provisioning, its implications for parent-offspring conflict, and conclude by considering the question of how hard provisioners should work.
44. YDENBERG, RC; WELHAM, CVJ; SCHMIDHEMPEL, R; SCHMIDHEMPEL, P; BEAUCHAMP, G. (1994) TIME AND ENERGY CONSTRAINTS AND THE RELATIONSHIPS BETWEEN CURRENCIES IN FORAGING THEORY.Behav. Ecol. 5: 28-34 TIME AND ENERGY CONSTRAINTS AND THE RELATIONSHIPS BETWEEN CURRENCIES IN FORAGING THEORY
EFFICIENCY; ENERGY GAIN; FORAGING STRATEGIES; PROVISIONING
Measured foraging strategies often cluster around values that maximize the ratio of energy gained over energy spent while foraging (efficiency), rather than values that would maximize the long-term net rate of energy gain (rate). The reasons for this are not understood. This paper focuses on time and energy constraints while foraging to illustrate the relationship between efficiency and rate-maximizing strategies and develops models that provide a simple framework to analyze foraging strategies in two distinct foraging contexts. We assume that while capturing and ingesting food for their own use (which we term feeding), foragers behave so as to maximize the total net daily energetic gain. When gathering food for others or for storage (which we term provisioning), we assume that foragers behave so as to maximize the total daily delivery, subject to meeting their own energetic requirements. In feeding contexts, the behavior maximizing total net daily gain also maximizes efficiency when daily intake is limited by the assimilation capacity. In contrast, when time available to forage sets the limit to gross intake, the behavior maximizing total net daily gain also maximizes rate. In provisioning contexts, when daily delivery is constrained by the energy needed to power self-feeding, maximizing efficiency ensures the highest total daily delivery. When time needed to recoup energetic expenditure limits total delivery, a low self-feeding rate relative,to the rate of energy expenditure favors efficient strategies. However, as the rate of self-feeding increases, foraging behavior deviates from efficiency maximization in the direction predicted by rate maximization. Experimental manipulations of the rate of self-feeding in provisioning contexts could be a powerful tool to explore the relationship between rate and efficiency-maximizing behavior. DOI
43. SCHMIDHEMPEL, P; WINSTON, ML; YDENBERG, RC. (1993) INVITATION PAPER (ALEXANDER,C.P. FUND) - FORAGING OF INDIVIDUAL WORKERS IN RELATION TO COLONY STATE IN THE SOCIAL HYMENOPTERA.Can. Entomol. 125: 129-160 INVITATION PAPER (ALEXANDER,C.P. FUND) - FORAGING OF INDIVIDUAL WORKERS IN RELATION TO COLONY STATE IN THE SOCIAL HYMENOPTERA
Workers of social insects are members of colonies that survive and reproduce together. Therefore, the behavioral activities of individual workers should be integrated with colony state. We here summarize and discuss the relationship between colony state and foraging behavior of individual workers under the provisional assumption that the colony is a unit. We argue that colony state can be described by a number of variables that should relate to fitness components in order to be meaningful. Among the possible candidates, colony population size seems to have an overriding importance in many respects, as shown by its relation to fitness components such as survival probability and reproductive performance. Other important variables include colony demography, i.e. caste or size distributions, nutritional status, or queen number. Each of these variables has been shown to affect fitness components; however, the evidence is rather scanty. We also discuss the evidence that variation in colony state variables relates to variation in individual worker behavior. Nutritional status (i.e. low or high levels of food stores) and colony size have been shown repeatedly to affect individual behavior. However, most of the evidence comes from the honey bee. Some studies suggest that behavioral responses are hierarchically structured. More work needs to be done to investigate the actual mechanisms of integration of individual behavior with colony state. Some knowledge has accumulated about the processes that govern recruitment to food sources. We conclude this review by discussing some concepts and problems for further research. These include the concept of a preferred colony state to which the colony should return after disturbance through the behavioral activities of the workers. Further theoretical elaboration and empirical investigations may help to elucidate whether this concept is useful and necessary. A largely neglected issue concerns the number versus effort problem, i.e. whether individuals should work harder or more workers should be allocated to a task that is in demand. We propose a simple scenario that suggests testable predictions. Finally, we discuss how colony state, individual work load, and the dependence of worker mortality rate on activity level may interact to generate different short-term foraging strategies that workers should adopt. DOI
42. STEEGER, C; YDENBERG, RC. (1993) CLUTCH SIZE AND INITIATION DATE OF OSPREYS - NATURAL PATTERNS AND THE EFFECT OF A NATURAL DELAY.Can. J. Zool.-Rev. Can. Zool. 71: 2141-2146 CLUTCH SIZE AND INITIATION DATE OF OSPREYS - NATURAL PATTERNS AND THE EFFECT OF A NATURAL DELAY
We studied the breeding performance of ospreys (Pandion haliaetus) in southeastern British Columbia from 1987 to 1990. Clutch size, brood size, and the number of young fledged per nest all declined significantly as clutch initiation date was delayed. The quality of later born young as measured by growth rate and the number of fault bars in rectrices did not seem to be reduced. Behavioural observations of the flight-hunting performance of six focal males demonstrated that food availability did not decline in the course of the nestling period. Clutch initiation of some osprey pairs was naturally delayed when their nests were occupied by Canada geese (Branta canadensis). Nest occupation delayed clutch initiation by 9.4 days on average, and reduced clutch size by 0.2 eggs. Osprey pairs possessing an alternate nest were not delayed by the presence of geese in their primary nest, and did not reduce clutch size, suggesting that the clutch size reduction was a direct response to the delay, rather than to the presence, of geese. The results do not support the reduced food availability or reduced breeding commitment hypotheses for seasonal clutch size decline. The data conform to the predictions of the hypothesis that the optimal clutch size is set by a trade-off between the declining reproductive value of later hatched nestlings and the delay required to be able to enlarge the clutch. DOI
41. WELHAM, CVJ; YDENBERG, RC. (1993) EFFICIENCY-MAXIMIZING FLIGHT SPEEDS IN PARENT BLACK TERNS.Ecology 74: 1893-1901 EFFICIENCY-MAXIMIZING FLIGHT SPEEDS IN PARENT BLACK TERNS
BLACK TERN; CENTRAL PLACE FORAGING; CHLIDONIAS-NIGRA; DAILY ENERGY EXPENDITURE; EFFICIENCY-MAXIMIZING; ENERGY; FLIGHT SPEED; FORAGING CURRENCIES; OPTIMAL FORAGING; RATE MAXIMIZING
Optimal foraging theory assumes that individuals maximizing a given energy currency maximize their fitness. Though models with different currencies (and assumptions) have been successful at describing forager behavior, discriminating among currencies has proven difficult because models optimizing different currencies often make similar predictions. A field experiment was designed to use flight speeds of Black Terns (Chlidonias nigra) feeding their young to test predictions from optimal foraging models that maximize (1) the net energy gained per unit of energy expended (efficiency; EFF), (2) the net rate of energy intake (NREI), and (3) the daily delivery rate (DR), respectively. Manipulating the distance an adult had to fly between a feeding enclosure and its nest enabled us to discriminate among the three currencies. Predicted speeds of the EFF model best matched the observed flight speeds. Maximizing efficiency resulted in the lowest delivery rate to the nest, but it was also the only currency that predicted adult daily energy expenditures within the theoretical limit (DEE(max)) estimated for Black Terns (206 kJ/d; Kirkwood 1983). The feeding enclosure represented an unusually profitable food source for the terns, and this may have resulted in artificially high predictions for flight speed, particularly for the NREI and DR currencies. We therefore made another set of predictions from the three models using estimates of foraging success from parents who had never foraged from the feeding enclosure, and compared these predictions with the measured airspeeds. The EFF model was apain the best predictor of flight speeds even though none of the three models predicted energy expenditures in excess of DEE(max). Though the DR model resulted in the highest total daily energy delivered to the nest, this represented only a small gain relative to the NREI and EFF models. Black Tem parents may maximize EFF because this currency is least likely to result in daily energy expenditures that exceed their metabolic limit. DOI
38. GUILLEMETTE, M; YDENBERG, RC; HIMMELMAN, JH. (1992) THE ROLE OF ENERGY-INTAKE RATE IN PREY AND HABITAT SELECTION OF COMMON EIDERS SOMATERIA-MOLLISSIMA IN WINTER - A RISK-SENSITIVE INTERPRETATION.J. Anim. Ecol. 61: 599-610 THE ROLE OF ENERGY-INTAKE RATE IN PREY AND HABITAT SELECTION OF COMMON EIDERS SOMATERIA-MOLLISSIMA IN WINTER - A RISK-SENSITIVE INTERPRETATION
COMMON EIDER; ENERGY INTAKE; PREY SELECTION; RISK-SENSITIVITY; BODY CONDITION
1. We measured prey selection and habitat profitability of common eiders Somateria mollissima L. wintering in the Gulf of St. Lawrence, Quebec, Canada. Prey selection was evaluated by comparing the frequency of prey in stomachs of shot eiders with their frequency in the sublittoral zone. Habitat profitability was estimated using information on time spent feeding, foraging success, diving durations and energy content of the prey. 2. In this region, eiders forage on a variety of prey types from several distinct habitats, kelp beds, urchin barrens and beds of the phaeophyte Agarum cribrosum (Mert.). In kelp beds eiders feed mostly on small blue mussels Mytilus edulis L. Over barrens they capture green sea urchins Strongylocentrotus droebachiensis (Muller), and over Agarum beds they feed on both spider crabs Hyas araneus (L.) and urchins. 3. Flock size also varies with habitat type: all sizes of flocks feed in the kelp beds, whereas mostly small flocks feed in the barrens and Agarum beds. Small-flock individuals strongly select mussels and crabs whereas urchins are non-preferred prey. 4. Dive and foraging cycles differ significantly according to the above three habitats. Although, the size, density and energy content of prey differ markedly between kelp and Agarum beds, these two habitats offer an even energy return. However, the variance in energy return in these two habitats differs strikingly, being greater in the latter. We hypothesized, in the context of risk foraging theory, that this was related to flock sizes and body condition. As predicted, individuals feeding in small flocks were in bad condition compared to individuals feeding in large flocks. This suggests that small-flock individuals are seeking the habitat offering a variable intake to improve their survival probability. DOI
37. MACHMER, MM; ESSELINK, H; STEEGER, C; YDENBERG, RC. (1992) THE OCCURRENCE OF FAULT BARS IN THE PLUMAGE OF NESTLING OSPREYS.Ardea 80: 261-272 THE OCCURRENCE OF FAULT BARS IN THE PLUMAGE OF NESTLING OSPREYS
We document the occurrence of fault bars in a population of nestling Ospreys Pandion haliaetus under natural conditions. Ospreys had an average of 9.9 fault bars on their rectrices, however variation was large. Fault bar formation declined linearly with age and increased symmetrically from outer to inner rectrices. Fault bar incidence is consistent in all plumage groups and those groups most essential for flight are least affected. We also examine fault bar occurrence in relation to two hypotheses: food shortage and handling effect. The former is investigated indirectly by comparing the number and intensity of rectrix fault bars in nestlings to their feeding rank and to their brood size. Neither variable has a significant effect on fault bar severity. The possibility of weather-mediated food shortage is examined, but no strong effect of weather is detected. The role of handling is assessed by comparing the number and intensity of fault bars in nestlings experiencing different numbers of nest visits. Nestlings visited repeatedly had more fault bars providing support for the handling hypothesis. Analysis of the timing of fault bar formation with respect to nest visits is suggestive as further evidence for the role of handling.
36. STEEGER, C; ESSELINK, H; YDENBERG, RC. (1992) COMPARATIVE FEEDING ECOLOGY AND REPRODUCTIVE-PERFORMANCE OF OSPREYS IN DIFFERENT HABITATS OF SOUTHEASTERN BRITISH-COLUMBIA.Can. J. Zool.-Rev. Can. Zool. 70: 470-475 COMPARATIVE FEEDING ECOLOGY AND REPRODUCTIVE-PERFORMANCE OF OSPREYS IN DIFFERENT HABITATS OF SOUTHEASTERN BRITISH-COLUMBIA
We compared the general breeding and feeding ecology of ospreys (Pandion haliaetus) in the Creston and Nelson areas of southeastern British Columbia. In the Creston Valley, ospreys nested atop tall trees surrounding a shallow and productive warm-water marsh. Prey species taken by male ospreys included black bullhead (Ictalurus melas), pumpkinseed (Lepomis gibbosus), and yellow perch (Perca flavescens). In contrast, near Nelson, ospreys nested on man-made structures along the narrow West Arm of Kootenay Lake. Osprey prey species in the Nelson area included longnose sucker (Catostomus catostomus), largescale sucker (Catostomus macrocheilus), and mountain whitefish (Prosopium williamsoni). Prey captured at Nelson were larger and contained significantly more energy than at Creston Valley, and hunting from a perch was used for 26 % of all captures. All Creston Valley prey were caught by flight hunting. The strike success of foraging ospreys at Nelson was significantly higher than at Creston, and the net yield of flight hunting was 3 times higher. In spite of these differences, the breeding performance of ospreys in the two areas was very similar. Average clutch size was 2.8, brood size at hatching was 2.0, and the average pair fledged 1.4 young. The nest failure rate did not differ between the two areas. Most clutches were initiated in early May. with Nelson-area ospreys laying, on average, 4-7 days later. Egg volumes were smaller at Nelson (66.6 vs. 69.1 cm3). However, the rate at which nestlings gained mass was significantly greater at Nelson. We discuss reasons why the breeding performance varies so little in spite of the great differences in feeding regime. DOI
35. BERTRAM, DF; KAISER, GW; YDENBERG, RC. (1991) PATTERNS IN THE PROVISIONING AND GROWTH OF NESTLING RHINOCEROS AUKLETS.AUK 108: 842-852 PATTERNS IN THE PROVISIONING AND GROWTH OF NESTLING RHINOCEROS AUKLETS
We studied (1983-1987) the provisioning and growth of nestling Rhinoceros Auklets (Cerorhinca monocerata) in a breeding colony on the Lucy Islands and measured growth (1984-1986) in other colonies also on the British Columbia coast (Pine Island and Triangle Island). There were strong differences in the pattern of provisioning among the three years. In 1985 provisioning peaked around the midpoint (30 days) of the nestling period and then declined rapidly. In 1986, provisioning also declined after the midpoint, but more slowly than in 1985. In 1987, provisioning remained approximately constant during the entire breeding season. We found no evidence that late-hatched chicks were consistently fed less than early-hatched chicks, though the statistical power of the tests made to detect this difference was low. There were significant annual differences in chick growth. Growth was fastest in 1985, intermediate in 1984 and 1986, and slowest in 1983 and 1987. The mean growth rate on the three colonies changed in unison from year to year. Hypotheses based on seasonal environmental changes and on systematic changes in the food requirements of growing chicks do not explain the observed patterns. Our data on chick growth and independent data on ocean production suggest that the two varied directly and in unison among years. However, provisioning in the latter part of chick development did not appear to reflect directly the quality of ocean feeding conditions. We conclude that although large-scale fluctuations in ocean production are likely to be the dominant influence upon provisioning, the manner in which parents respond to such variation is poorly understood.
33. YDENBERG, R; GUILLEMETTE, M. (1991) DIVING AND FORAGING IN THE COMMON EIDER.ORNIS SCANDINAVICA 22: 349-352 DIVING AND FORAGING IN THE COMMON EIDER
We recorded the duration of successive dives and pauses during sequences of foraging by wintering Common Eiders Somateria mollissima in the Gulf of St. Lawrence. The length of each pause on the surface between dives increases at an increasing rate with the length of the preceding dive. Based on this relationship, the deviation from the estimated surface time (DEVEST, for short) was computed for each dive. DEVEST is positively correlated over short series of dive-cycles. The significance of these results is discussed and compared with an earlier study on Western Grebes Aechmophorus occidentalis. DOI
