Philopatry and Dispersal within a Black Guillemot Colony

-We studied patterns of dispersal and philopatry within a Black Guillemot (Cepphus grylle) colony, based on a 22-year capture-recapture study of individually-marked birds. The study colony in western Iceland was divided into 15 subcolonies. Out of 356 local recruits, 122 settled in their natal subcolony, a far higher proportion than expected from a random distribution. The western part of the colony attracted significantly more recruits than did the eastern part. Breeding dispersal among subcolonies only occurred in one percent of all cases in which a bird was captured in two successive years. We suggest that potential recruits select their breeding site based on an assessment of quality as expressed by conspecific breeding success, and also that philopatry occurs because this information acquisition is less than perfect and birds bias their search towards their natal site. Received 18 May 1998, initially accepted 24 November 1998, final acceptance 15 May 1999.