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Demographic parameters were estimated for snow petrels Pagodroma nivea nesting at Pointe Géologie Archipelago, Adélie Land, Antarctica between 1963 and 1990; 21 years of data on adult survival and 27 years of data on breeding success are available. The average age of first return and first breeding were 8.1 and 9.9 years respectively and there was no signifcant difference between the sexes. The overall breeding success averaged 51.3% and was very variable between years (21-80%). Breeding failure was mostly due to incubation failure and annual breeding success was negatively correlated with average snow falls in October-November and October-March. Breeding frequency was very low, averaging 52% of seasons during a reproductive lifetime. Good quality sites, with high occupancy rate and high breeding success were few in the study plots. Poor years in 1966-1967, 1976-1977 and 1983-1984, with low breeding success, very low proportions of nets with breeding attempts and high numbers of non-breeders, occurred 1 year after large-scale El Niño Southern Oscillation (ENSO) events. Snow petrels exhibited very low philopatry. Only 45 birds have been recovered in the study plots from a total of 1115 banded fledglings giving an estimated rate of return of 12.9% between fledging and 3 years old. Annual survival between 3 and 10 years was 91.4%. Annual adult survival (93.4%), though variable, was low during poor years of 1977-1978 and 1983-1984. Adult survival of males (94.7%) was not significantly different from that of females (93.9%). Over the study period, the population of Pointe Géologie was stable. Using the estimated parameters, a Leslie model gave a growth rate of 0.948%, which was probably compensated by immigration (5.7% per year). Restricted numbers of good-quality sites at the place of birth could have led young birds to prospect other colonies and could have selected low philopatry. High adult survival, strong site tenacity and capacity to spread breeding over a long lifetime are probably part of the adaptive strategy of this small fulmarine petrel facing highly variable environmental conditions.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 203.64.11.45 on Mon, 06 Apr 2015 12:24:08 UTC All use subject to JSTOR Terms and Conditions Abstract. 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 Thinbilled Prion (Pachyptila belcheri, a neritic feeder), and the Common Diving Petrel (Pelecanoides 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.