Foraging movements of Magellanic Penguins Spheniscus magellanicus in the Beagle Channel, Argentina, related to tide and tidal currents

RAYA REY, A.; BOST, CH.-A.; SCHIAVINI, A.; PÜTZ, K

INTERNATIONAL JOURNAL OF ORNITHOLOGY

Springer

Lugar: Heidelberg; Año: 2010 vol. 151 p. 933 - 943

1519-888X

This study investigates the movements ofMagellanic Penguins Spheniscus magellanicus breedingon Isla Martillo during the early chick-rearing period.Foraging paths were reconstructed using GPS loggers thatregistered the penguins0 geographic position, water temperatureand depth at regular intervals. The relationshipbetween penguins0 movements and search strategies, tideand tidal currents were assessed. Mean trip duration was onaverage 14.7 ± 6.9 h (33% overnight), and the maximumdistance reached was 24 ± 10 km. All penguins studiedforaged to the east of the colony. We identified threephases based on the sinuosity and speed of the trajectory:transit, central and return. Foraging effort was higherduring the central phase, followed by the transit phase, andlower in the return phase. Foraging success, measured asthe percentage of time at the bottom during each phase,was also highest during the central phase. In all birdsstudied, the central phase of the foraging trip took placeduring ebb tide, and birds travelled to the foraging areaswith flow tide running in the same direction of displacement.Our study suggests that penguins take advantage oftidal currents to facilitate their movements to and from themain foraging area, thereby reducing the energy expended.Moreover, we suggest that piscivorous diving birds mayenhance their catch rate during ebb tide when fish are moreconcentrated near the channel bed.