Intersexual differences in the diving behaviour of Imperial Cormorants

AGUSTINA GÓMEZ LAICH; FLAVIO QUINTANA; EMILY L.C.SHEPARD; RORY P. WILSON

Journal of Ornithology

© Dt. Ornithologen-Gesellschaft e.V. 2011

Año: 2011 vol. XX p. 1 - 9

1439/0361

Intersexual differences in the foraging behaviour have been examined in several seabird species, especially those exhibiting sexual size dimorphism. We studied intersex behavioural differences in the Imperial Cormorant(Phalacrocorax atriceps), a size dimorphic seabird. Twenty adults (11 females and 9 males), breeding at Punta León (43°40´S; 64° 20 ´W), Chubut, Argentina, were equipped with loggers to measure tri-axial acceleration and depth, to calculate the foraging trip time/activity budgets and diving behaviour. Both sexes had similar foraging trip durations, spending a similar proportion of the foraging time flying and floating on the sea surface. However, females spent more time underwater, executing more and shallower dives. Females also recovered more quickly than males from dives performed to depths of less than 30 m and spent more time foraging along the bottom at any depth than males. We conclude that if allometric effects affect the foraging behaviour of Imperial Cormorants, they only do so during diving because no differences were observed in the total amount of time sexes spent flying or foraging.