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

Analyses of the body masses of Adelie penguins (Pygoscelis adeliae) departi ng 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 t he guard stage than at the end and both sexes gained similar amounts of bod y mass during the creche period. Results support the hypothesis that the fo raging effort of Adelie penguins at Bechervaise Island is partitioned betwe en the sexes, with males accepting a net rate of negative energy gain to pr ovide regular meals for their offspring during the guard stage. Adelie peng uin 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 tha t previously postulated for some species of flying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Maws on region of eastern Antarctica is discussed in relation to micronekton dis tribution in the area.