Egg size, temperature and laying sequence: Why do Snow Geese lay big eggs when it's cold?
Back to previous page
| Authors: | Williams, TD; Cooch, EG |
| Year: | 1996 |
| Journal: | Functional Ecology 10: 112-118 |
| Title: | Egg size, temperature and laying sequence: Why do Snow Geese lay big eggs when it's cold? |
| Abstract: | 1. Several studies of altricial passerines ('income breeders') have shown that females lay smaller eggs when they experience low temperatures during egg formation, This is usually explained in terms of a 'physiological trade-off': birds having to divert more of their finite resources to maintenance and away from reproduction in cold weather, although little is known about the proximate mechanism(s) underlying this phenomenon. 2. We investigated the relationship between egg size and ambient temperature during egg formation period in the Lesser Snow Goose (Anser caerulescens caerulescens), a precocial, 'capital-breeding' species, using 10 years of data derived from a long-term. population study of this species at La Perouse Bay, Man., Canada. 3. Egg size was negatively correlated with ambient temperature in the Snow Goose, i.e. females laid larger eggs when temperatures were lower during egg formation, contrasting markedly with the positive correlation reported in altricial, income-breeders. 4. The effect of temperature on egg size was most marked for last-laid eggs within a clutch (b = 0.675 g degrees C-1), and for temperatures during the last half of the rapid yolk development (RYD) period (rather than for the whole or the middle of the RYD period), as predicted by an exponential growth curve for yolk development. 5. The relationship between egg mass and temperature was time- and laying-sequence specific: for first and middle eggs the correlation was positive early in the period of RYD and negative closer to ovulation. For last-laid eggs the correlation between egg mass and temperature was negative throughout the 10 day RYD period. 6. We suggest that the different relationship between egg size and temperature in the Snow Goose, compared to passerine species, may reflect different contributions of exogenous vs endogenous reserves, and different opportunities to increase energy availability through dietary intake. 7. Although statistically significant, temperature has only a small effect on egg size in the Lesser Snow Goose: the average range of temperatures encountered would only lead to a 3-5% difference in mean egg mass, This is consistent with high heritability of egg size. |
Please send suggestions for improving this publication database to
sass-support@sfu.ca.
Departmental members may update their publication list.