Individual variation in workload during parental care: can we detect a physiological signature of quality or cost of reproduction?
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| Authors: | Williams, TD; Fowler, MA |
| Year: | 2015 |
| Journal: | Journal of Ornithology 156: S441-S451 Article Link (DOI) |
| Title: | Individual variation in workload during parental care: can we detect a physiological signature of quality or cost of reproduction? |
| Abstract: | How hard do birds work during parental care, chick rearing, or provisioning of their nestlings? And if birds do work hard, can we detect a physiological signature of individual variation in workload ability (perhaps related to 'quality') or costs associated with high workload? Here, we provide a broad conceptual perspective on these questions. Life-history theory predicts (or requires) that (1) parental care is hard work, (2) individuals that invest more in parental care benefit in terms of rearing more, larger, fitter offspring, but that (3) increased investment in parental care comes at a cost: decreased future fecundity and/or survival. However, we start by highlighting studies that are inconsistent with this conventional view, e.g., (1) females often do not pay a survival cost of increased workload (though males do), (2) some (high quality?) individuals appear to maximise numerous life-history traits, and (3) workload during parental care often does not predict productivity. We suggest that an "exercise physiology" perspective on parental care might be informative, but highlight the fact that existing models of exercise often involve conditions very different from that free-living animals experience while foraging (e.g., using forced exercise) and are often divorced from the critical relationship in free-living animals between exercise and acquisition of resources. We briefly review studies looking at physiological effects of workload during parental care in freeliving birds, but again highlight our surprising lack of knowledge in this area especially where experimental manipulation of workload is coupled with comprehensive, physiological analysis. Finally, we make three recommendations for how can we advance the study of physiology of parental care in chick-rearing birds: (1) experimental manipulation of workload, (2) obtaining better measures of workload, for large numbers of known-individuals, and (3) better assessment of physiology of individual quality, and identification of specific metrics of workload-induced 'wear and tear'. |
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