“Long days, long trips: foraging ecology of female rockhopper penguin brooding chicks at Tierra del Fuego”

A SCHIAVINI; A RAYA REY

MARINE ECOLOGY PROGRESS SERIES

Inter-Research

Lugar: Oldendorf/Luhe, Germany; Año: 2004 vol. 275 p. 251 - 262

0171-8630

Abstract: We studied the foraging ecology of female southern rockhopper penguin brooding chicks at Bahía Franklin (Staten Island) during December 2000. We compared our data with data presented for other subspecies and locations, analyzing the features of the foraging ecology and its relationship with the environment, the daylight period around Staten Island, and the population size of different breeding locations. Southern rockhopper penguins performed longer trips (about 30% and 60% longer for daily and overnight trips respectively) and between 5 and 7 more overnight trips (53%) than the northern and eastern subspecies.  Mean dive depth and dive duration were 28.9 ± 24.6 m and 79 ± 30 s respectively. The diving rate (30.4 ± 5.0 dives h-1), and the proportion of trip duration underwater (66.2 ± 5.9%) confirmed the high foraging effort of rockhopper penguins. During the study period the foraging trip duration increased, but dive parameters did not vary. Penguins traveled as much as 20 km to the foraging waters, either in shelf waters and/or in waters of a close shelf break and slope. The diet was dominated in numbers by euphausids, amphipods, cephalopods, fish larvae and juveniles, all prey species commonly found in Subantarctic waters. The long trips would be explained by the long twilight period and by diel vertical migration of prey, confirming the phenotypic plasticity of penguins in response to different marine environments. The extended foraging trip duration may contribute to sustain the large level of the breeding population (167,000 breeding pairs). This would also help to understand the different recent history of breeding colonies at the southwestern Atlantic Ocean.