Social Dominance in Young White-Throated Sparrows: Effects of Early Social Experience and the Unstable Period

Abstract

ABSTRACr.-I examined the influence of early social experience on winter dominating ability in White-throated Sparrows (Zonotrichia albicollis). Eleven sparrows from four broods were hand raised to independence, housed in flocks with their brood mates for 8 to 9 weeks, placed in isolation or in a flock of six for an additional 17 weeks (the experimental phase), and then tested for in one of three juvenile flocks consisting of unfamiliar hand-reared birds and wild-caught birds. The mass of a nestling relative to its brood mates was not correlated with its final dominance, and no dominance interactions were observed between nestlings. Similarly, although an unstable period occurred in the brood-mate flocks during which dominance relationships fluctuated greatly from day to day, neither dominance status nor total number of dominance interactions in the brood-mate flocks was correlated with final dominance. In contrast, social conditions imposed during the experimental phase appeared to influence final dominance strongly. Three of five isolates achieved the top rank in final flocks, sparrows from the experimental flock were all of low rank, and wild-caught sparrows attained intermediate rank. These results suggest that the social conditions experienced by juvenile White-throated Sparrows before they leave the breeding ground and during fall migration might have a lasting effect on their dominance status and, thus, their survival in winter. Received 14 October 1994, accepted 5 April 1995.