Journal
POLAR BIOLOGY
Volume 32, Issue 1, Pages 27-33Publisher
SPRINGER
DOI: 10.1007/s00300-008-0498-9
Keywords
Diet; Foraging specialisation; Mixing models; Scavenging
Categories
Funding
- Department of Employment and Learning Northern Ireland
- NERC
- NERC [bas010017, lsmsf010002] Funding Source: UKRI
- Natural Environment Research Council [bas010017, lsmsf010002, ceh010023] Funding Source: researchfish
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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 (13)C values hatched chicks earlier than those with depleted (13)C values. Individuals with enriched (13)C 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 delta(13)C 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.
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