Phenotypic correlates and consequences of dispersal in a metapopulation ofhouse sparrows Passer domesticus

1. We examine causes and consequences of natal dispersal within a metapopul ation of house sparrows Passer domesticus in an archipelago in Northern Nor way when a large proportion of the individuals is colour-ringed. 2. Less than 10% of the fledglings dispersed, i.e. left their natal island. 3. Dispersal was female biased and almost exclusively performed by juvenile s. 4. The probability of natal dispersal was not related either to the body co ndition or the body mass of the juvenile. Similarly, neither clutch size no r hatching date explained a significant proportion of the variance in the p robability of dispersal. 5. The probability of male natal dispersal was related to the rank of the f ledgling in the size-hierarchy within the brood. Low ranking individuals th at hatched early in the season were more likely to disperse. 6. In both sexes, the survival of dispersers at the island of establishment was higher than among the residents on that island. Similarly, dispersers survived better than adults that remained on their island of birth. 7. These results suggest that dispersal may be an adaptive strategy to avoi d poor conditions in the natal area.