Diet, individual specialisation and breeding of brown skuas (Catharacta antarctica Ionnbergi): an investigation using stable isotopes

Anderson, O.R.J., Phillips, R.A., Shore, R.F., McGill, R.A.R. , McDonald, R.A. and Bearhop, S. (2009) Diet, individual specialisation and breeding of brown skuas (Catharacta antarctica Ionnbergi): an investigation using stable isotopes. Polar Biology, 32(1), pp. 27-33. (doi:10.1007/s00300-008-0498-9)

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Abstract

The diet of brown skuas (Catharacta antarctica lonnbergi) on Bird Island, South Georgia was assessed using a combination of stable isotope analysis (SIA) and mixing model techniques. We found evidence that individual specialisation in diet of adult brown skuas was related to timing of breeding, which may reflect differences in intrinsic quality. Adults with more enriched 13C values hatched chicks earlier than those with depleted 13C values. Individuals with enriched 13C fed predominantly on Antarctic fur seal (Arctocephalus gazella) carrion and placenta while those with lower ratios appeared to rely more on burrowing petrels (e.g. Antarctic prions Pachyptila desolata). Individual foraging differences clearly influenced timing of breeding and potentially the reproductive output of breeding pairs. We confirmed that the main components of the diet of brown skuas during incubation are, in decreasing order of importance, Antarctic fur seal placenta, burrowing petrels and fur seal muscle. In addition, we identified fur seal faeces in the diet during this stage, which had not been detected previously by traditional sampling methods. Finally we identified a correlation in δ13C values between pair members, attributable to the influence of courtship feeding of females by males, or assortative mating according to foraging preference or intrinsic quality.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:McGill, Dr Rona
Authors: Anderson, O.R.J., Phillips, R.A., Shore, R.F., McGill, R.A.R., McDonald, R.A., and Bearhop, S.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Polar Biology
Publisher:Springer Verlag
ISSN:0722-4060
ISSN (Online):1432-2056
Published Online:29 July 2008

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