Differential rates of offspring provisioning in Gould’s petrels: are better feeders better breeders?

Procellariiformes (albatrosses and petrels) must accumulate substantial energy reserves to sustain them while incubating their single egg. They then produce a chick that is often more than 130% of their own body mass. Thus, despite the variable nature of resource availability in the marine environment, successful reproduction requires a considerable increase in foraging rates. Birds that are better foragers are, therefore, likely to be better parents. As surrogates of foraging ability, we assessed two parental traits that are separated temporally over the breeding season, body condition during incubation and provisioning performance, in Gould’s petrel (Pterodroma leucoptera). Although parental condition did not influence hatching success, we found significant positive correlations between the average body condition of a breeding pair and both the growth rate of chicks (g day^–1) and the body condition of chicks at peak mass. Provisioning rate also correlated positively with chick condition. Chick condition was positively correlated with haemoglobin concentration [Hb] at peak mass, which was positively correlated with [Hb] at fledging. Because the probability of survival after fledging may be influenced by chick body condition and [Hb], the ability of parents to acquire additional resources for breeding is likely to be an important determinant of reproductive success.