Original Paper

Polar Biology

, Volume 32, Issue 1, pp 27-33

First online:

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

  • O. R. J. AndersonAffiliated withSchool of Biological Sciences, MBC, Queen’s University Belfast Email author 
  • , R. A. PhillipsAffiliated withBritish Antarctic Survey, Natural Environmental Research Council
  • , R. F. ShoreAffiliated withCentre for Ecology and Hydrology, Lancaster Environment Centre
  • , R. A. R. McGillAffiliated withScottish Universities Environmental Research Centre
  • , R. A. McDonaldAffiliated withCentral Science Laboratory
  • , S. BearhopAffiliated withSchool of Biological Sciences, MBC, Queen’s University BelfastCentre for Ecology and Conservation, School of Biosciences, University of Exeter

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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.


Diet Foraging specialisation Mixing models Scavenging