NO EVIDENCE FOR EXTRA-PAIR PATERNITY IN THE WESTERN GULL

The genetic mating system of western gulls Larus occidentalis breeding on Southeast Farallon Island, California, was determined using multil ocus DNA fingerprints of 33 chicks from 22 broods. No extra-pair pater nity (EPP) was found, despite extra-pair copulations (EPCs) occurring. This suggests that paternity guards are effective, and that females g ain few genetic benefits from EPCs. The EPP in western gulls concurs w ith that of other seabirds, reinforcing the idea that seabirds general ly have a monogamous genetic mating system.