Hormone-Behavior Adaptations in Arctic Birds

北极的夏季给候鸟带来了许多问题，这些候鸟利用苔原丰富的生产力进行繁殖。繁殖期是如此短暂，以至于建立领地、配对和求偶所需的时间可能被缩短到几天甚至几个小时。鸟类必须早到开始筑巢，这样幼鸟就能在有利于它们生存的条件下产卵。通常，北极春季的天气条件非常恶劣，导致严重的代谢问题，不仅影响到繁殖的开始，甚至影响到生存。这项研究将阐明北极鸟类抵御北极夏季严酷气候的机制。这些问题包括：为什么在物种之间和物种内部肾上腺皮质对压力的反应会有差异？这是否与应激激素（如皮质酮）的行为影响和神经组织中受体的分布有关？这种差异是否通过性腺激素的作用受到光周期的调节。此外，我们还将探讨白冠麻雀在到达时表现出空间机会主义，然后既不保卫领地也不保卫巢穴的繁殖策略变异的激素基础；在雪中，猎食表现出一种中间策略，至少在产卵期间保护巢穴，但在季节的后期似乎没有领土。这些物种的比较以及类固醇激素在大脑中的受体分布将为北极鸟类激素行为适应的多样性提供新的线索，并对脊椎动物生殖过程的调节具有重要意义。这两个目标都与极地生物学和医学的项目目标相一致。

The Arctic summer poses a number of problems for migratory birds that exploit the rich productivity of the tundra for reproduction. The breeding period is so brief that the time required for the establishment of a territory, pair bonding and courtship may be truncated into a few days or even hours. Birds must arrive early to begin nesting so that the young are produced while conditions are still favorable for their survival. Frequently, weather conditions in the Arctic spring are severe, resulting in serious metabolic problems not only for the onset of breeding but even for survival. This research will elucidate the mechanisms by which Arctic birds resist the rigors of the Arctic summer. Among the questions addressed are why there is variation in the adrenocortical responsiveness to stress both among and within species, whether this is related to behavioral effects of stress hormones such as corticosterone and the distribution of receptors in neural tissue, and whether the variability is regulated by photoperiod through the action of gonadal hormones. Additionally, the hormonal basis of variation in breeding strategy will be explored in the white-crowned sparrow that shows spatial opportunism on arrival and then defends neither a territory nor a nest site; and in the snow bunting that shows an intermediate strategy and defends a nest site at least during egg-laying, but does not appear to be territorial later in the season. Comparisons of these species, and receptor distributions for steroid hormones in the brain will shed new light on the diversity of hormone-behavior adaptations in Arctic birds, and will have considerable significance for the regulation of reproductive processes of vertebrates in general. Both of these objectives are alligned with program goals for Polar Biology and Medicine.