Seasonal changes in the diet and feeding behaviour of a top predator indicate a flexible response to deteriorating oceanographic conditions
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Shifts in the diet of top predators can be linked to changes in environmental conditions. In this study, we tested relationships between environmental variation and seasonal changes in diet of a top predator, the grey-headed albatross Thalassarche chrysostoma, breeding at Bird Island, South Georgia in an austral summer of 1999/2000. Oceanographic conditions in that year around South Georgia were abnormal (i.e. anomalously high sea surface temperature to a relative 19-year long-term mean). The diet of grey-headed albatrosses showed high seasonal variation, shifting from cephalopods (42.9 % by mass) in late February to Antarctic krill Euphausia superba (58.3 %) in late April, and grey-headed albatrosses breeding performance was low (16.8 %). This study shows these albatrosses did not manage to find sufficient alternative prey and highlight the risk to top predators if there is an increase in the frequency or severity of food shortages in Antarctic waters.
KeywordsAntarctic Peninsula Antarctic Circumpolar Current Oceanographic Condition Antarctic Water Antarctic Polar Front
We thank Bird Island staff especially Simon Berrow, Richard Humpidge, Nik Aspey and Mark Jessop for help in collecting the samples, Simon Berrow and Robert Taylor for useful discussions on the field protocol, Rachael Shreeve for valuable advice on crustacean identification and Filipe Ceia, Jaime Ramos and Vitor Paiva for statistical discussions. We are particularly grateful to Paul Rodhouse and Phil Trathan for their advice through the project. This research was initially evaluated by an ethical committee, and it was supported by the Ministry of Science and Technology, Portugal (Fundação para a Ciência e a Tecnologia; FCT) and by the British Antarctic Survey, UK. J.X. was funded by FCT, and M.L. was funded by a Marie Curie Individual Fellowship (PIEF-GA-2008-220063) and Juan de la Cierva postdoctoral programme (JCI-2010-07639, Ministerio de Ciencia e Innovación ). The altimeter products were produced by Ssalto/Duacs and distributed by Aviso, with support from Cnes (http://www.aviso.oceanobs.com/duacs/).
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