Hormone-Behavior Adaptations in Arctic Birds

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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.