Environmental effects and life-history variation in birds

父母在塑造子女方面起着至关重要的作用。母亲尤其可能通过产前激素或抗体的转移和（或）产后护理影响后代。当母亲经历压力环境时，其后代可能表现出与无压力母亲的后代不同的生理和行为。传统上，这被视为不良养育环境的非适应性后果。一个新出现的观点是，母亲实际上是在调整自己的后代，以更好地应对随后的环境挑战。产前和产后线索对塑造后代的相对重要性已经在实验室动物中进行了研究，但直到最近才在野外进行了研究。*我提出的研究的主要目标是用野生鸟类来测试产前和产后母亲的暗示是否会以一种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)产前激素提示在塑造后代特征方面的作用是什么？它们是否提高了存活率？(2)母鼠是否在不同温度下孵卵以调整后代的特征？(3)压力是否会影响母亲将抗体传递给后代的能力，以及她是否会根据环境中病原体的数量调整自己的反应？*为了测试问题1和问题2，我们将研究环嘴鸥。我们建议在受干扰程度不同的鸥群区域之间交换蛋。“不匹配”的雏鸡将在产前收到一种程度的干扰（通过它们的蛋）的母体线索，但将在不同程度的干扰中长大；“匹配”的雏鸡将被饲养在它们产卵的同一区域（受到相同程度的干扰）。如果产前提示导致雏鸡的适应性调整，我们预测“不匹配”环境下的雏鸡将比“匹配”环境下的雏鸡质量更低，存活率更低。“不匹配”雏鸟的母亲在第二年的回报率会更低。我们还将通过实验控制鸡蛋的皮质酮水平（母体压力的激素提示），将圈养的小鸡暴露在不同形式的压力下，并在接下来的一年测量它们的行为和生理。*从理论上讲，母亲也可以使用卵子孵化温度作为调节后代的机制（问题2）。为了验证这一点，我们将远程监测实验压力/非压力母亲的巢穴温度。我们预测压力大的母亲产下的卵会经历更大的温度波动。如果被干扰的孵化行为是母亲塑造后代的一种机制，我们预测，与未被干扰的巢穴相比，来自被干扰巢穴的雏鸟对压力的反应会更迟钝。这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压力荷尔蒙信号发挥作用。*母亲可以将抗体转移到她们的卵子中，有可能表现出对某一性别的偏爱。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，我们将比较温带种群和亚热带种群的蛋的抗体水平，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，当受到压力时，温带地区的雌性会比亚热带地区的雌性（那里有更多的病原体）传递更少的抗体，这对温带地区的后代产生负面影响。如果母性压力限制了雌性在产前传递抗体的能力，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.