Breeding-stage related sex differences in the foraging behaviour of Magellanic Penguins

RAYA REY A; K PÜTZ; SCIOSCIA G; B LÜTHI; SCHIAVINI A

EMU

CSIRO PUBLISHING

Año: 2012 p. 90 - 96

0158-4197

Understanding the foraging behaviour of seabirds and its plasticity is vital to establish their role in marine foodwebs and their use as indicators of change in the availability of prey. The foraging behaviour of penguins is known to differwith locality, sex, stage of breeding and between years. We studied the diving behaviour of breeding Magellanic Penguins(Spheniscus magellanicus), using time-depth recorders, during incubation and brooding in the 2003?04 and 2004?05breeding seasons at Isla Martillo, Tierra del Fuego, Argentina. Foraging trips during the incubation period were longer thanthose during the brooding period for both sexes in both years of the study. Sex-related differences in foraging behaviour wereobserved during the incubation stage. During the incubation stage females performed longer foraging trips than males,foraging effort was lower, and did not dive as deep as males in both years. Foraging success was lower for females than malesduring incubation only in 2003. Our results suggest that sexual differences, expressed as differences in the foragingparameters of males and females, only develop when Fuegian Sprat (Sprattus fuegensis), the main prey in this locality, is notabundant close to the colony. Females may be extending the volume of water they can exploit by extending the duration oftrips (horizontal distance), whereas males do so by diving deeper (vertical distance). Our results show the fundamentaldifferences in foraging strategies between the sexes in Magellanic Penguin are a consequence of environmental conditionsnot morphological differences between sexes.