Effects of Dispersal Date on Winter Flock Establishment and Social Dominance in Marsh Tits Parus palustris

(1) We studied the effect of sex, size, age and prior occupancy on social dominance winter flock establishment in a population of marsh tits Parus palustris L. (2) When sex was accounted for, time of establishment in the winter flock-prior occupancy, was critical for the outcome of later aggressive interactions juveniles within flocks. Residents won all interactions with intruders irrespective controlling for sex. (3) Success in, and timing of, establishment were closely linked with hatching lower proportion of late-hatched than early-hatched juveniles became established winter flocks; they also became established later. Even small differences in hatching greatly influenced dominance and the probability of becoming established flock. (4) Since early establishment depends on early hatching, dominance and survival juveniles are determined by how early their parents start breeding. Furthermore, will be strong selection for quick establishment after