Environmental effects, thermal energetics, and avian life history variation

母亲通过胚胎发育期间的荷尔蒙信号和/或通过调整出生后护理，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使用野生和圈养鸟类来了解母亲是否以一种适应性的方式为她们的后代做好准备，以应对预测的环境变化。我和我的学生将回答三个一般性的问题：(1)如果母亲在产卵前经历热浪，它们的雏鸟是否更有能力应对未来的高温？(2)母亲是否会调整沉积在鸡蛋中的甲状腺激素水平，作为一种机制，为雏鸟为未来的气温做准备？(3)成年鸟类喂养雏鸟的能力是否受到过热风险的限制，以及在发育过程中，母亲的暗示是否会提高过热的温度？为了测试问题1，我们将在产卵前将圈养鸟类暴露在模拟热浪中。然后，我们将在与它们母亲经历的温度“匹配”或“不匹配”的环境中饲养雏鸟。我们预测，如果母亲能通过出生前的暗示为雏鸟的热生理做好准备，那么与那些经历了温度不匹配的雏鸟相比，匹配的雏鸟将有更快的生长速度，并将更好地应对热浪。为了测试问题2和3，我们将研究野生树燕。我们将试验性地提高鸡蛋中的甲状腺激素水平，并在试验性降温环境中饲养雏鸟。众所周知，甲状腺激素可以加快生长速度和新陈代谢。我们预测，在胚胎时期暴露于甲状腺激素的雏鸟在暴露在寒冷中时将表现出较低的生理压力水平。由于母亲可能会将不同数量的荷尔蒙沉积到卵子中，我们还将研究这是否可能是母亲调整个体雏鸟的大小等级和竞争优势的机制。为了测试问题3，我们将通过实验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，具有更强的散热能力的父母将增加它们的活动量和雏鸟的喂食率。为了测试饲养环境是否会改变热极限，我们将训练目标1中的鸟类在高温下锻炼。我们预测，母亲在产卵前经历热浪的后代将在高温下保持更高的活动，但可能会经历高活动的生理代价。总体而言，这项研究将有助于了解母亲是否能够调整子女的能力，以应对预测的温度变化，并确定可能的荷尔蒙机制。这项拟议的研究将提供关键的生理学数据，供研究人员和管理人员在预测种群和物种应对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.