Foraging movements of Magellanic Penguins Spheniscus magellanicus in the Beagle Channel, Argentina, related to tide and tidal currents |
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Authors: | Andrea Raya Rey Charles-André Bost Adrián Schiavini and Klemens Pütz |
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Institution: | (1) Consejo Nacional de Investigaciones Cient?ficas y T?cnicas, CADIC, Bernardo Houssay 200, (V9410BFD), Ushuaia, Tierra del Fuego, Argentina;(2) Centre d’?tudes Biologiques de Chiz?, Centre National de la Recherche Scientifique, 79360 Villiers en Bois, France;(3) Wildlife Conservation Society, 2300 Southern Blvd, Bronx, NY 10460, USA;(4) Antarctic Research Trust, PO Box 685, Stanley, FIQQ 1ZZ, Falkland Islands |
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Abstract: | This study investigates the movements of Magellanic Penguins Spheniscus magellanicus breeding on Isla Martillo during the early chick-rearing period. Foraging paths were reconstructed using GPS loggers that
registered the penguins′ geographic position, water temperature and depth at regular intervals. The relationship between penguins′
movements and search strategies, tide and tidal currents were assessed. Mean trip duration was on average 14.7 ± 6.9 h (33%
overnight), and the maximum distance reached was 24 ± 10 km. All penguins studied foraged to the east of the colony. We identified
three phases based on the sinuosity and speed of the trajectory: transit, central and return. Foraging effort was higher during
the central phase, followed by the transit phase, and lower in the return phase. Foraging success, measured as the percentage
of time at the bottom during each phase, was also highest during the central phase. In all birds studied, the central phase
of the foraging trip took place during ebb tide, and birds travelled to the foraging areas with flow tide running in the same
direction of displacement. Our study suggests that penguins take advantage of tidal currents to facilitate their movements
to and from the main foraging area, thereby reducing the energy expended. Moreover, we suggest that piscivorous diving birds
may enhance their catch rate during ebb tide when fish are more concentrated near the channel bed. |
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