BODY CONDITION AND SEABIRD REPRODUCTIVE-PERFORMANCE - A STUDY OF 3 PETREL SPECIES

We investigated relationships between body condition (body mass scaled by body size) early in the breeding season and reproductive performance of three seabird species showing various life history traits. The study was conducted at Kerguelen Island from 1987 to 1994 on the Blue Petrel (Halobaena caerulea, an oceanic feeder), the Thin-billed Prion (Pachyptila belcheri, a neritic feeder), and the Common Diving Petrel (Pelecanoides up urinatrix, a coastal feeder). Breeding success was highly variable among years in the three species, but the proportion of nonbreeding experienced breeders varied significantly only in the Blue Petrel. In the three species, body condition showed considerable year-to-year variation, suggesting substantial fluctuation in the availability of prey early in the breeding season. Relationships between early body condition and reproductive performance differed among the species. Reproductive success was significantly influenced by early condition in the Blue Petrel but not in the Thin-billed Prion and the Common Diving Petrel. In the long-lived Blue Petrel, depletion of body condition early in the breeding season resulted in a high proportion of nonbreeders and massive egg desertion. On the other hand, the shorter lived Thin-billed Prion and Common Diving Petrel seemed to respond by maintaining their reproductive output during poor years, probably investing more in the reproductive episode. Such contrasted patterns are analyzed in the light of reproductive effort and optimal clutch size theory.