Influence of body condition on reproductive decision and reproductive success in the Blue Petrel

Following the prediction that body condition affects whether eggs are laid in birds, we examined variations in prebreeding body condition (i.e. body mass one month before laying, adjusted for structural size, breeding experience, and date of return), incidence of breeding, and reproductive success of male and female Blue Petrels (Halobaena caerulea). Condition was inversely correlated with date of return and positively related to breeding experience in males, but not in females. In both sexes, condition displayed year-to-year variations; the 1991-1992 season was distinguished by poor condition, low incidence of breeding, and low reproductive success. Condition in both males and females, and breeding experience in males had significant effects on the ''decision to breed.'' Breeding experience also influenced the decision to breed, especially in males. Condition, but not breeding experience, had a significant influence on male incubation success. Female breeding performances were not related to condition but to breeding experience. Annual average breeding success was highly variable and significantly correlated with male condition. Prebreeding visits appeared to be critical for this pelagic seabird and may allow individuals, through their condition, to manage their reproductive investment. We suggest that condition mainly affects egg formation in females and, together with breeding experience, influences the duration and the quality of prebreeding colony attendance in males. The potential relationships of body condition, breeding experience, reproductive investment, and future survival are discussed.