Partitioning of foraging effort in Adelie penguins provisioning chicks at Bechervaise Island, Antarctica

Analyses of the body masses of Adelie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and < 40 h, respectively) during chick rearing showed that the departure weights of birds prior to long trips were significantly lighter than were those prior to short trips. Penguins, particularly males, were significantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of body mass during the creche period. Results support the hypothesis that the foraging effort of Adelie penguins at Bechervaise Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals for their offspring during the guard stage. Adelie penguin foraging behaviour may be driven by a trade-off between the allocation of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of flying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica is discussed in relation to micronekton distribution in the area.