High-latitude environments impose constraints on breeding activities of migratory birds which necessitate adjustments to a much shorter season. Environmental constraints may have been met by adaptations of the endocrine system which serve to fine-tune breeding activities to suit arctic conditions. It is proposed that the endocrine systems of polar nesting birds display decreased sensitivity to stimuli that would result in rapid and disruptive elevations of hormones which could affect breeding or nesting activities at inappropriate times. The roles of two potentially antagonistic hormones will be examined: testosterone, which elicits territorial aggression; and corticosterone, which can act to inhibit reproductive activities including territorial aggression. The endocrine adaptations to be investigated in this research program may elucidate physiological mechanisms by which polar animals avoid delays and/or conflicting behaviors which might reduce chances for successful reproduction.
