Demographic influences of translocated individuals on a resident population of house sparrows

Translocation of individuals from source populations to augment small populations facing risk of extinction is an important conservation tool. Here we examine sex-specific differences between resident and translocated house sparrows Passer domesticus in reproductive success and survival, and the contribution of translocated individuals to the growth of a local population. We found evidence for assortative mating based on origin revealed by fewer parentages between translocated males and resident females than expected, and the total number of fledglings produced by such pairs was lower. Interestingly, the reproductive success of translocated males was positively related to the size of the throat badge (a sexual ornament), such that translocated males with a large badge size were as successful as resident males. However, offspring with parents of different origin had higher survival than offspring with parents of same origin, which suggests hybrid vigour. The contribution of resident and ...