Determinants of Feeding Chases in the Chinstrap Penguin Pygoscelis antarctica

Abstract

Feeding interactions between parents and chicks in pygoscelid penguins are frequently associated with chases. We tested alternative predictions derived trom two functional hypotheses proposed to explain feeding chases: (1) the harassment of the parent by two begging, competing chicks is stressful and makes the parent run away to avoid stress (‘harassment avoidance hypothesis’) and (2) chases are initiated by parents to separate the two chicks before feeding them in order to avoid inter-sibling competition, and thus to increase food transfer efficiency (‘efficient food transfer hypothesis’). In an observational study of Chinstrap Penguins Pygoscelis antarctica during the crèche stage, we found that feeding chases were initiated in the presence of two begging chicks independently of their competitive disposition. When the chicks competed, parental visits lasted longer, and parents took longer time to transfer a given number of feedings, than when there was no competition. In chases inducing chick separation, the duration of adult running bouts was determined by the time it took to separate them. This would not be the case if feeding chases were initiated to avoid harassment by two competing chicks. Feeding chases initiated by parents appears to be a behaviour tending to separate the two chicks in order to feed them more efficiently, which results in shortening the time spent by parents in the colony. Additionally, we found some evidence indicating that through the feeding chases parents could also gain information on the nutritional needs of their chicks.