Costs of switching social groups for dominant and subordinate dark-eyed juncos (Junco hyemalis)

Abstract

I quantified the costs of switching from a familiar to an unfamiliar flock for captive dark-eyed juncos (Junco h. hyemalis) by measuring several physiological and behavioral variables before and after flock switching. Birds that were initially dominant dropped in status in unfamiliar flocks, and experienced increased metabolic rates, while subordinate birds appeared to undergo less physiological change when switching flocks. This difference occurred despite a lack of any rank-related differences in the effects of joining a new flock on rates of aggression, weight change, access to food, or plasma corticosterone levels. These results suggest that for dominant, but not subordinate, individuals there is a measurable metabolic cost to joining a new social group, even in the absence of adverse factors such as food limitation. Dominant individuals may be less likely than subordinates to leave familiar flocks because of their higher metabolic costs when joining a new social group.