Parental foraging effort and offspring growth in Adelie Penguins: does working hard improve reproductive success?

1. Studying variability of parental foraging and provisioning behaviour in relation to reproductive success is fundamental to improving understanding of regulation of reproductive effort in animals. The hypothesis that parents with higher foraging effort have higher offspring growth rates was tested in chick-provisioning Adelie Penguins in Antarctica over five consecutive years. 2. Time spent diving per day, an index of foraging effort, varied among male and female parents, and among pairs. These daily interindividual or interpair differences in time spent diving appeared to be consistent over the 2-week study period within each breeding season. 3. Frequency of meals delivered by parents was positively correlated with their brood growth rate. Meal frequency was, however, independent of the amount of time spent diving per day by parents and the time spent diving did not affect brood growth rates. 4. Rates of body mass loss of breeding pairs were positively correlated with brood growth rates. 5. Our results did not support the hypothesis that parents with higher foraging effort have higher offspring growth rates. It is suggested that parental allocation of resources obtained during foraging, rather than the degree of foraging effort, is the more important process determining offspring growth rates in Adelie Penguins.