Cooper Caren B, Voss Margaret A
Bird Population Studies, Cornell Lab of Ornithology, Ithaca, New York, United States of America.
PLoS One. 2013 Jun 19;8(6):e65521. doi: 10.1371/journal.pone.0065521. Print 2013.
Incubation conditions for eggs influence offspring quality and reproductive success. One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance. Age related changes in embryo thermal tolerance would thus be expected to shape parental incubation behavior. We use data from unmanipulated Black-capped Chickadee (Poecile atricapillus) nests to examine the temporal dynamics of incubation, testing the prediction that increased heat flux from eggs as embryos age influences female incubation behavior and/or physiology to minimize temperature fluctuations. We found that the rate of heat loss from eggs increased with embryo age. Females responded to increased egg cooling rates by altering incubation rhythms (more frequent, shorter on- and off- bouts), but not brood patch temperature. Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature. Our findings highlight the need to view full incubation as more than a static rhythm; rather, it is a temporally dynamic and finely adjustable parental behavior. Furthermore, from a methodological perspective, intra- and inter-specific comparisons of incubation rhythms and average egg temperatures should control for the stage of incubation.
卵的孵化条件会影响后代质量和繁殖成功率。亲鸟调节育雏条件的一种方式是，在胚胎的热需求与为了自身维持而离开巢穴的时间之间取得平衡。因此，胚胎耐热性的年龄相关变化预计会塑造亲鸟的孵化行为。我们使用来自未受操控的黑顶山雀（Poecile atricapillus）巢穴的数据来研究孵化的时间动态，检验随着胚胎发育，卵的热通量增加会影响雌鸟的孵化行为和/或生理机能，从而使温度波动最小化这一预测。我们发现，卵的散热速率随着胚胎发育而增加。雌鸟通过改变孵化节奏（更频繁、更短的进出巢周期）来应对卵冷却速率的增加，但育雏斑温度没有变化。因此，随着胚胎发育，雌鸟能够提高卵的平均温度并减少温度变化。我们的研究结果凸显了将整个孵化过程视为不仅仅是一种静态节奏的必要性；相反，它是一种随时间动态变化且可精细调节的亲代行为。此外，从方法论的角度来看，孵化节奏和平均卵温的种内和种间比较应考虑孵化阶段。
