Attendance of breeders and prospectors reflects the duality of colonies in the Kittiwake Rissa tridactyla

Attendance of breeders and prospectors (prebreeders, failed breeders and non-breeding adults) was studied from the time of hatching to the end of the breeding season in parts of two neighbouring Kittiwake Rissa tridactyla colonies in Brittany (France). Many clutches in one subcolony had been predated by a Carrion Crow Corvus corone, leading to a lower breeding success. Attendance of breeders and prospecting activity were greater in the more successful colony, and the number of breeding pairs increased in the following year in this colony only. Local reproductive success and social behaviour contributed to the attraction exerted by a colony. The demographic trend was explained by a performance-based conspecific attraction mechanism, acting through the effect of local reproductive success on recruitment, non-breeding and fidelity. Study of breeding success and prospecting activity allowed both evaluation of the quality of a colony and prediction of local demographic trends for the following year.