Changes in depth utilization in relation to the breeding stage: a case study with the King Penguin Aptenodytes patagonicus

The impact of breeding constraints on foraging strategies of penguins has been poorly studied. We examined during two years the foraging behaviour of King Penguins Aptenodytes patagonicus during the incubating, brooding and creching periods at the Crozet Islands, southern Indian Ocean. In this species, the non-synchronized breeding cycle makes possible the simultaneous study of foraging behaviour at two breeding stages, thus allowing a comparison of different foraging activities at constant food availability. Diving behaviour was assessed using time-depth recorders. When compared with birds with eggs, birds at the brooding stage dived deeper and spent more time at greater depth in summer, whereas their foraging trip duration was halved. In autumn, foraging trip duration, depth attained and diving frequency to depth >100 m for birds with small and large chicks were generally greater than those observed in birds foraging in summer. The significance of these changes is discussed with respect to breeding requirements and food availability.