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1 April 2016 Environmentally-Mediated Flexible Foraging Strategies in Brown Boobies in the Gulf of California
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The Brown Booby Sula leucogaster is a seabird with a pantropical distribution across a wide variety of oceanic environments. Sexual size dimorphism in Brown Boobies has been proposed as an explanation for intersexual differences in foraging, but results have been inconsistent. We investigated whether there is context-dependent foraging behaviour driven by local environmental conditions. In this study, we evaluated (1) inter-sex differences in foraging behaviour (by capillary tubes, temperature and depth recorders, and diet) at two colonies in the Gulf of California: Isla San Jorge (ISJ) and Farallón de San Ignacio (FSI) and, (2) intercolonial and interannual differences in foraging behaviour, and (at ISJ) their relationship with local-scale environmental variation, using 5-day composite images of sea surface temperature (SST) and primary productivity (PP) as proxies. Inter-sex differences were few and inconsistent between years, and smaller than overall differences between years and localities. At ISJ, Brown Boobies included more prey species in their diet (27 vs. 19 spp.) and dove shallower (2.3 vs. 3.14 m) than at FSI. At ISJ, Brown Boobies exhibited adjustments in diving depth and prey size as a function of environmental variation: shallower plunge dives and smaller prey items were related with lower SST and higher PP values, whereas deeper dives and larger prey items were related with higher SST and lower PP values. Our results confirmed that the Brown Booby is highly plastic in its foraging ecology, which explains its ability to live in places with large-scale environmental variation (intercolony and interannual), such as tropical areas worldwide.

José Alfredo Castillo-Guerrero, Miriam Lerma, Eric Mellink, Edith Suazo-Guillén, and Erik A. Peñaloza-Padilla "Environmentally-Mediated Flexible Foraging Strategies in Brown Boobies in the Gulf of California," Ardea 104(1), 33-47, (1 April 2016).
Received: 11 November 2014; Accepted: 1 January 2016; Published: 1 April 2016

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