This study proposes to examine the hormone-behavior adaptations that maximize survival and reproductive success in birds breeding in the extreme conditions of the high Arctic. The focus will be on a typical high Arctic seabird, the Dovekie (Alle alle), and two typical arctic passerines, the Lapland Longspur (Calcarius lapponicus) and Snow Bunting (Plectrophenax nivalis). Temporal patterns of testosterone, breeding condition, and reproductive success will be studied, as well as adrenocortical responses to environmental stress. Field studies will be conducted in northern Greenland using Thule AFB as a logistical staging area. This will be the first study in the region using these techniques and and logistical capabilities. Because these techniques are inherently risky and the logistical demands are extreme, the PIs have chosen to submit a proposal of limited scope under the guidelines of the Small Grants for Exploratory Research (SGER) program.