Environmental effects and life-history variation in birds

父母在塑造后代方面起着关键作用。 特别是母亲可能通过产前激素或抗体的转移和/或通过产后护理来影响后代。 当母亲经历压力环境时，后代可能会表现出与非压力母亲后代不同的生理和行为。 传统上，这被认为是不良饲养环境的非适应性后果。 一个新的观点是，母亲实际上是在调整自己的后代，以更好地科普随后的环境挑战。 关于产前和产后线索在塑造后代方面的相对重要性，人们已经在实验室动物身上进行了研究，但只是最近才在野外进行。我提出的研究的主要目标是利用野生鸟类来测试产前和产后的母性暗示是否会以适应性的方式改变后代的生理和行为。 在我提出的研究中，我和我的学生将解决三个一般性问题：（1）产前激素暗示在塑造后代特征方面的作用是什么，它们是否增加了存活率？(2)母亲会在不同的温度下孵蛋来调整后代的特征吗？(3)压力是否会影响母亲将抗体转移给后代的能力？她是否会根据环境中的病原体数量调整自己的反应？为了测试问题1和2，我们将研究环嘴鸥。 我们建议在干扰程度不同的海鸥群区域之间交换蛋。 “不匹配的”小鸡将接收到一种干扰水平的产前母体线索（通过它们的蛋），但将在不同的干扰水平下饲养;“匹配的”小鸡将在它们产蛋的殖民地的相同区域（和相同的干扰水平）饲养。 如果产前线索导致小鸡的适应性调整，我们预测小鸡从“不匹配”的环境将是较低的质量和较低的生存比小鸡从“匹配”的环境。 “不匹配”的小鸡的母亲在第二年的回报率会更低。 我们还将实验性地操纵鸡蛋的皮质酮水平（母性压力的激素线索），将圈养的小鸡暴露在不同形式的压力下，并在第二年测量它们的行为和生理。从理论上讲，母亲也可以使用鸡蛋孵化温度作为调整后代的机制（问题2）。 为了测试这一点，我们将远程监测实验压力/非压力母亲的巢温。 我们预测，有压力的母亲的卵子会经历更大的温度波动。 如果中断孵化行为是母亲塑造后代的一种机制，我们预测，与未受干扰的巢中的小鸡相比，受干扰的巢中的小鸡将表现出对压力的迟钝反应。 这种情况是如何发生的尚不清楚，但我们将测试胚胎是否通过产生自己的荷尔蒙应激信号来发挥作用。母亲可以将抗体转移到她们的卵子中，并有可能表现出对一种性别的偏爱。 母亲也可以根据环境中病原体的数量来分配抗体。 使用树燕，我们将比较来自温带种群和亚热带种群的卵的抗体水平，并测试雏鸟对免疫挑战的反应能力是否不同（问题3）。 我们预测，当强调，温带女性将转移较少的抗体比亚热带女性（那里有更多的病原体），温带后代的负面影响。 如果母亲的压力限制了女性产前转移抗体的能力，可能会对经历环境退化和新出现疾病威胁的人群产生负面影响。

Parents play a critical role in shaping their offspring. Mothers in particular may influence offspring via prenatal transfer of hormones or antibodies and/or via postnatal care. When mothers experience stressful environments, offspring may display differing physiologies and behaviours from offspring of non-stressed mothers. Traditionally, this has been viewed as a non-adaptive consequence of a poor rearing environment. An emerging perspective is that mothers are in fact adjusting their offspring to better cope with subsequent environmental challenges. The relative importance of pre and postnatal cues in shaping offspring has been studied in laboratory animals, but only recently in the wild.* The major goal of my proposed research is to use wild birds to test whether pre- and postnatal maternal cues change offspring physiology and behaviour in an adaptive way. In my proposed research, my students and I will address three general questions: (1) What is the role of prenatal hormonal cues in shaping offspring characteristics, and do they increase survival? (2) Do mothers incubate their eggs at different temperatures to adjust offspring characteristics? (3) Does stress impact a mother's ability to transfer antibodies to her offspring, and does she adjust her response to the number of pathogens in the environment?* To test questions 1 and 2, we will study ring-billed gulls. We propose to swap eggs between regions of a gull colony that differ in levels of disturbance. "Mismatched" chicks will receive prenatal maternal cues of one level of disturbance (via their egg), but will be raised in a different level of disturbance; "Matched" chicks will be reared in the same area of the colony in which their eggs were laid (and same level of disturbance). If prenatal cues result in adaptive adjustments in the chicks, we predict chicks from "mismatched" environments will be of lower quality and have lower survival than chicks from "matched" environments. The mothers of "mismatched" chicks will have lower return rates the following year. We will also experimentally manipulate egg corticosterone levels (a hormonal cue of maternal stress), expose captive chicks to differing forms of stress, and measure their behaviour and physiology the following year.* Theoretically, mothers may also use egg incubation temperature as a mechanism to adjust their offspring (Question 2). To test this, we will remotely monitor nest temperatures of experimentally stressed/non-stressed mothers. We predict that eggs of stressed mothers will experience greater fluctuations in temperature. If disrupted incubation behaviour is a mechanism for mothers to shape their offspring, we predict chicks from disturbed nests will show a blunted response to stress when compared with chicks from non-disturbed nests. How this occurs is not known, but we will test whether embryos play a role via producing their own hormonal cues of stress.* Mothers can transfer antibodies to their eggs, with potential to show favouritism to one sex over the other. Mothers may also allocate antibodies according to the number of pathogens in the environment. Using tree swallows, we will compare antibody levels of eggs from temperate populations with subtropical populations, and test whether nestlings differ in their ability to respond to an immune challenge (Question 3). We predict that when stressed, temperate females will transfer fewer antibodies than will sub-tropical females (where there are more pathogens), with negative consequences for temperate offspring. If maternal stress limits a female's ability to transfer antibodies prenatally, there may be negative consequences for populations that experience combinations of environmental degradation and the threat of emerging diseases.