Energetics and avian life-history trade-offs

动物的种类和种群在生长速度、繁殖力和其他生活史特征方面差别很大。理解生命史策略多样性的基础是认识到各种特征之间存在权衡。最主要的取舍是繁殖的“成本”；在当前的繁殖努力和未来的适应性之间。例如，当喂养依赖的幼崽时，父母可能会通过降低免疫功能和/或夜间代谢率来抵消白天的高能量消耗。这种代偿性调节的生理机制在很大程度上仍然未知。我建议使用圈养的鸟类来确定潜在的代谢和激素机制，从而减少夜间代谢。了解可能限制个体对白天能量消耗增加的反应的生理机制，对于预测种群对环境扰动的反应至关重要。通常，恶劣的环境条件会导致繁殖的鸟类无法满足后代的食物需求，从而产生潜在的负面健康后果。为了使后代更好地适应当前的环境条件，父母似乎能够通过发育过程中的信号（例如，鸡蛋的营养含量或抗体水平）来改变后代的生理机能。我提出的研究的第二个主要组成部分是确定这些信号如何/何时可能增加后代的适应性。以鹌鹑为例，我建议测试出生前后蛋白质限制对成年后在不同环境中饲养的个体的适应性的影响。平行的实地研究将测试病原体压力的地理差异是否会影响雌性向后代转移的产前抗体水平，以及水平是否会受到母体压力的负面影响。如果产妇压力升高限制了产前抗体传播，可能会对面临环境退化和新出现疾病威胁的人群产生负面影响。

Species and populations of animals differ widely in growth rate, fecundity and other life-history traits. Fundamental to understanding diversity in life-history strategies is the recognition that trade-offs exist among various traits. The dominant trade-off is the "cost" of reproduction; that between current reproductive effort and future fitness. For example, when feeding dependent young, parents may offset high daytime energy expenditure by reducing, among other things, immune function and/or overnight metabolic rate. The physiological mechanisms underlying such compensatory adjustments remain largely unknown. I propose to use captive birds to identify potential metabolic and hormonal mechanisms enabling reductions in overnight metabolism. Understanding the physiological mechanisms that may constrain an individual's response to increased daytime energy expenditure is critical to predicting how populations will respond to environmental perturbations. Frequently, poor environmental conditions can result in breeding birds being unable to meet offspring food demands, with potentially negative fitness consequences. To better match their offspring to prevailing environmental conditions, parents appear able to modify offspring physiology, via signals during development (e.g., egg nutrient content or antibody levels). The second major component of my proposed research is to determine how/when such signals might increase offspring fitness. Using quail, I propose to test the effect of pre and postnatal protein limitation on the subsequent fitness of individuals when they are reared in variable environments as adults. Parallel field studies will test whether geographic variation in pathogen pressure influences the levels of prenatal antibodies females transfer to offspring, and whether levels are influenced negatively by maternal stress. If elevated maternal stress constrains prenatal antibody transmission, there may be negative implications for populations experiencing combined environmental degradation and the threat of emerging diseases.