Environmental effects, thermal energetics, and avian life history variation

母亲通过胚胎发育期间的激素信号和/或通过调整产后护理，在塑造其后代的生理方面发挥着关键作用。我提出的研究的主要目标是利用野生和圈养鸟类来了解母亲是否以适应性的方式引导后代，以科普预测的环境变化。我和我的学生将回答三个一般性问题：（1）如果母亲在产卵前经历了热浪，那么它们的雏鸟是否能够更好地科普未来的高温？(2)母亲是否会调整沉积在卵中的甲状腺激素水平，以此作为雏鸟适应未来温度的一种机制？(3)成年鸟类喂养雏鸟的能力是否受到过热风险的限制？在发育过程中，母亲的暗示是否会增加过热发生的温度？为了测试问题1，我们将在产卵前将圈养的鸟类暴露在模拟热浪中。然后，我们将在与母亲所经历的温度“匹配”或“不匹配”的环境中抚养雏鸟。“我们预测，如果母亲可以通过产前暗示来启动雏鸟的热生理，那么“匹配”的雏鸟将有更快的生长速度，并且能够比那些经历过“不匹配”温度的雏鸟更好地科普热浪。为了测试问题2和3，我们将研究野生树燕。我们将实验性地增加蛋中的甲状腺激素水平，并在实验性的冷却环境中饲养雏鸟。已知甲状腺激素可提高生长速度和新陈代谢。我们预测，雏鸟暴露于甲状腺激素作为胚胎将显示较低水平的生理压力时，暴露于寒冷。由于母亲可能会将不同数量的激素存款到蛋中，我们还将研究这是否可能是母亲调整个体雏鸟大小等级和竞争优势的机制。为了测试问题3，我们将实验性地提高繁殖鸟类的散热能力，并使用自动无线电遥测系统测量飞行活动。我们预测，父母的散热能力增加，将增加他们的活动和雏鸟喂养率。为了测试饲养环境是否会改变热极限，我们将训练目标1中的鸟类在高温下运动。我们预测，其母亲在产卵前经历过热浪的后代将在高温下保持较高的活动，但可能会经历高活动的生理代价。总的来说，这项研究将有助于了解母亲是否能够调整其后代的能力，以科普预测的温度变化，并确定可能的激素机制。拟议的研究将提供关键的生理数据，供研究人员和管理人员在预测种群和物种科普气候变化的能力时使用。

Mothers play a critical role in shaping the physiology of their offspring, via hormonal signals during embryonic development and/or via adjustment of postnatal care. The major goal of my proposed research is to use wild and captive birds to understand whether mothers prime their offspring in an adaptive way, to cope with predicted environmental change. My students and I will address three general questions: (1) If mothers experience heat waves prior to egg laying, are their nestlings better able to cope with high temperatures in the future? (2) Do mothers adjust levels of thyroid hormones deposited in their eggs as a mechanism to prime nestlings for future temperatures? (3) Is the ability of adult birds to feed their nestlings limited by the risk of overheating, and can the temperature at which overheating occurs be increased by maternal cues during development? To test question 1, we will expose captive birds to simulated heat waves prior to egg laying. We will then raise nestlings in environments that "match" the temperature their mother experienced or are "mismatched." We predict that if mothers can prime a nestling's thermal physiology via prenatal cues, then "matched" nestlings will have faster growth and will be better able to cope with heat waves than those that experienced "mismatched" temperatures. To test questions 2 and 3, we will study wild tree swallows. We will experimentally increase thyroid hormone levels in eggs and raise nestlings in experimentally cooled environments. Thyroid hormones are known to increase growth rates and metabolism. We predict that nestlings exposed to thyroid hormones as embryos will display lower levels of physiological stress when exposed cold. Because mothers may deposit different amounts of hormone into eggs, we will also study whether this may be a mechanism by which mothers adjust the size hierarchy and competitive advantage of individual nestlings. To test question 3, we will experimentally increase the ability of breeding birds to dissipate heat and measure flight activity using an automated radio-telemetry system. We predict that parents with an increased capacity to dissipate heat will increase their activity and nestling feeding rates. To test whether thermal limits may be modified by the rearing environment, we will train birds from Objective 1 to exercise in the heat. We predict that offspring whose mothers experienced heat waves prior to egg laying will maintain higher activity in the heat but may experience physiological costs of high activity. Overall, this research will help understand whether mothers are able to adjust the capacity of their offspring to cope with predicted temperature change and identify possible hormonal mechanisms. The proposed research will provide key physiological data that can be used by researchers and managers when predicting the capacity for populations and species to cope with climatic change.