Abstract
The effects of changes in breeding success on nest-site tenacity and mate fidelity of Cory's Shearwater were examined in a colony on an island off Corsica. On average 84.3% of males and 75.7% of females kept the same site from year to year. When they changed nest-site birds moved mainly inside their own subcolony. The median distance between sites was 8 m for both males and females. A high turnover rate of breeders in the same nest-site was associated with a low breeding success in that birds tended to change mates and/or sites after a failure.