Diet and long-term changes in population size and productivity of brown skuas Catharacta antarctica lonnbergi at Bird Island, South Georgia

Phillips, R.A.; Phalan, B.; Forster, I.P.. 2004 Diet and long-term changes in population size and productivity of brown skuas Catharacta antarctica lonnbergi at Bird Island, South Georgia. Polar Biology, 27 (9). 555-561. 10.1007/s00300-004-0633-1

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Abstract/Summary

Breeding ecology of brown skuas (Catharacta antarctica lonnbergi) was studied at Bird Island, South Georgia in the austral summers of 2000/2001-2003/2004. A complete census recorded 467 breeding pairs in 3.55 km(2) of suitable habitat (132 pairs per km(2)), and an additional 312 nonbreeders at club-sites. Comparison with previous counts indicates two phases of population change: an initial rapid increase (3.6% per annum) from the late 1950s to early 1980s, probably attributable to increased carrion availability from the expanding Antarctic fur seal (Arctocephalus gazella) population, followed by slower growth (0.9% p.a.). Currently, seal carrion dominates the diet of skuas during incubation, with a switch to seabird prey during chick-rearing. Breeding is now later, chick growth poorer, and productivity significantly lower than in the early 1980s. There is also a strong seasonal decline in adult attendance, and chicks that hatch later and are in poorer condition are less likely to fledge. These results suggest a long-term increase in competition for carrion that is particularly apparent once fur seal pupping has ceased.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1007/s00300-004-0633-1
Programmes:	BAS Programmes > Independent Projects
ISSN:	0722-4060
NORA Subject Terms:	Zoology Ecology and Environment
Date made live:	23 Jan 2012 15:51 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/12340

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