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首页> 外文期刊>Journal of Field Ornithology: A Journal of Ornithological Investigation >Body mass variation in breeding Florida scrub-jays
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Body mass variation in breeding Florida scrub-jays

机译：Body mass variation in breeding Florida scrub-jays

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Many birds lose mass when feeding dependent young and multiple hypotheses have been proposed to explain this loss. The reproductive-stress hypothesis suggests that mass loss results from an energy deficit. The flight-efficiency hypothesis suggests that breeders lose mass in advance of feeding young to save energy during flight. The reserve-mobilization hypothesis suggests that female breeders accumulate energy reserves during egg production and incubation and mobilize those reserves to meet their own energy needs after eggs hatch. Finally, birds may lose mass due to gonadal regression. From 1999 to 2001, we attracted Florida Scrub-Jays (Aphelocoma coerulescens), sedentary cooperative breeders, to a portable electronic balance. Our objective was to determine which hypotheses might best explain mass variation during breeding. Both male and female Florida Scrub-Jays lost mass during the period of nestling care (males, 3.2; females, 6.5), but not when feeding fledglings, despite this being the period of peak effort. Such results are consistent with both the flight-efficiency and reserve-mobilization (females only) hypotheses. We also found a significant negative influence of brood size on mass change in males, providing support for the reproductive-stress hypothesis, and we conclude that, for males, both the flight-efficiency and reproductive-stress hypotheses apply. For female scrub-jays, our results were consistent with the flight-efficiency and energy-reserve mobilization hypotheses, both of which view mass loss as beneficial.

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