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Marine Ecology Progress Series

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MEPS 611:203-214 (2019)  -  DOI:

A sex-influenced flexible foraging strategy in a tropical seabird, the magnificent frigatebird

Rhiannon E. Austin1,2,*,**, Federico De Pascalis1, John P. Y. Arnould3, Jane Haakonsson4, Stephen C. Votier2, Gina Ebanks-Petrie4, Tim Austin4, Greg Morgan5, Georgia Bennett1, Jonathan A. Green1

1School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK
2Environment and Sustainability Institute, University of Exeter, Penryn TR10 9FE, UK
3School of Life and Environmental Sciences, Burwood Campus, Deakin University, Burwood, VIC 3125, Australia
4Department of Environment, Cayman Islands Government, Grand Cayman, KY1-1002, Cayman Islands
5RSPB, Ramsey Island, St Davids, Pembrokeshire SA62 6PY, UK
*Corresponding author: **née Meier

ABSTRACT: To successfully exploit resources, animals must be adapted to operate under phenotypic and environmental constraints. The strategies that predators use to locate prey are therefore diverse, particularly for breeding central-place foragers that must balance investment in reproduction and self-maintenance. Magnificent frigatebirds Fregata magnificens are tropical seabirds with intriguing morphology and feeding ecology, which display strikingly unequal levels of parental care (males deserting offspring months before females). These unusual traits can better help us understand the links between movement behaviour and breeding strategies in this poorly studied species. Using archival GPS, GPS-GSM loggers, bird-borne cameras and dietary data, we investigated the foraging ecology of chick-rearing magnificent frigatebirds from a breeding population in the Cayman Islands. This population engages in 2 main foraging strategies: (1) coastal trips over the continental shelf, where individuals target reef species and engage in kleptoparasitism, and (2) offshore trips during which birds feed on schooling pelagic prey. Differences in strategy use were partially linked to sex, with males (which invest less in offspring) roaming further from nests, and showing a higher propensity to forage offshore. Video data further indicated differences in social information use between strategies: foraging with conspecifics was more prevalent in coastal environments than pelagic. We suggest that observed variation in at-sea behaviour may partially be mediated by sex-based differences in parental roles, and/or size differences leading to intraspecific competition. Our study provides evidence of bimodal foraging and sheds new light on the importance of both pelagic and coastal feeding in this enigmatic species.

KEY WORDS: Fregata magnificens · Tracking · Seabird · Feeding ecology · Video logger

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Cite this article as: Austin RE, De Pascalis F, Arnould JPY, Haakonsson J and others (2019) A sex-influenced flexible foraging strategy in a tropical seabird, the magnificent frigatebird. Mar Ecol Prog Ser 611:203-214.

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