Ecology, behavior and endocrinology of an alpine breeding bird, the grey-crowned rosy finch (Leucosticte tephrocotis)

Arctic and alpine environments are often considered ecological equivalents in introductory textbooks, conservation planning and even in the primary literature. Both alpine and Arctic regions are cold, treeless expanses with low levels of grass- and forb-based primary productivity and simplified food webs. Furthermore, both environments are highly seasonal, with most to all of the productivity occurring during a short, snowfree period. Concomitant with the summer productivity is an influx of migratory fauna, and the emergence of hibernating species. Few studies, however, have made a critical comparison of these superficially similar environments. Arctic and alpine areas have some very clear differences, including energy regimes, proximity to benign refugia and the scale of the habitat. Birds breeding in both environments show seasonal modulation of the glucocorticoid response to unpredictable stressors. However, the pattern of this modulation is different. Arctic birds have a high stress response during the pre-breeding phase which tapers off as the breeding season progresses, while alpine-breeding birds have a damped stress response during pre-breeding which increases during the breeding phase, and then declines again during parental care. Birds in the two habitats also behave differently to unpredictable snowstorms while on the breeding grounds. Arctic birds remain on the breeding grounds during short-lived storms. Some alpine birds also remain on the breeding grounds; however, others descend to lower elevations for foraging. Seasonal patterns of sex steroid secretion are also different between birds in the two habitats. Arctic birds have peaks in circulating testosterone that last for less than one week, followed by varying degrees of testosterone insensitivity, while alpine birds have peaks that last for over one month. The behavioral and endocrinological differences seen in birds inhabiting the two environments suggests that there are some vital differences in these areas. Three major differences between Arctic and alpine environments are the proximity to refugia, the length of the breeding season and the predictability and variability of the climate. All three factors are likely interacting to cause the observed differences in physiology and behavior.