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Marine Ecology Progress Series

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MEPS 391:267-278 (2009)  -  DOI:

Species- and sex-specific differences in foraging behaviour and foraging zones in blue-footed and brown boobies in the Gulf of California

Henri Weimerskirch1,*, Scott A. Shaffer2, Yann Tremblay2, Daniel P. Costa2, Hélène Gadenne1, Akiko Kato3,6, Yan Ropert-Coudert3,6, Katsufumi Sato4, David Aurioles5

1Centre d’Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique, 79360 Villiers en Bois, France
2Ecology & Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California 95060, USA
3National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo 173-8515, Japan
4International Coastal Research Center, Ocean Research Institute, The University of Tokyo, 2-106-1 Akahama, Otsuchi, Iwate 028-1102, Japan
5Departamento de Pesquerias y Biologia Marina, CICIMAR-IPN, La Paz, B.C.S., Mexico
6Present address: Institut Pluridisciplinaire Hubert Curien, Centre National de la Recherche Scientifique,67037 Strasbourg, France

ABSTRACT: When 2 closely related species co-occur, each exhibiting sex-specific differences in size, resource partitioning is expected. We studied sex-specific foraging behaviour of 2 sympatric seabird species in the Gulf of California to disentangle the respective influence of species and sex, but also mass and size of individuals, on observed foraging behaviour. We used highly accurate data loggers to study movements, diving behaviour and activity of brown and blue-footed boobies rearing young chicks. Interspecific differences were limited; brown boobies had longer foraging trips and spent less time on the water than blue-footed boobies. The major differences observed were sex-specific; females of each species tended to have longer foraging trips, foraged farther from the colony, flew greater distances and had larger zones of area-restricted search. These sex-specific differences were more prominent in brown than in blue-footed boobies. Diet and stable isotope analyses showed that, during the study period, both species fed mainly on sardines, at similar trophic levels and in similar zones; outside the breeding season, the carbon and nitrogen signatures from feathers were also similar on average. In these sympatric species that feed on a superabundant prey, sex-specific differences appear to have a greater role than species-specific differences. We suggest that sex-specific differences may be mainly related to breeding involvement, as males are more involved in nest attendance and defence and females are greater provisioners. However, we show that several sex-specific differences in observed foraging behaviour were partly or totally explained by body size (flight speeds, foraging range, flapping frequency) or by body mass (depths attained during diving, duration of dives), which are parameters influenced by biomechanical constraints such as flight and diving.

KEY WORDS: Accelerometers · GPS tracking · Sula leucogaster · Sula nebouxii · Area-restricted search · Fractal landscape method · Diet · Isotopes

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Cite this article as: Weimerskirch H, Shaffer SA, Tremblay Y, Costa DP and others (2009) Species- and sex-specific differences in foraging behaviour and foraging zones in blue-footed and brown boobies in the Gulf of California. Mar Ecol Prog Ser 391:267-278.

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