Species

Justification
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Taxonomic source(s)
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Christidis, L.; Boles, W. E. 1994. The taxonomy and species of birds of Australia and its territories. Royal Australasian Ornithologists' Union, Melbourne.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
SACC. 2006. A classification of the bird species of South America. Available at: http://www.museum.lsu.edu/~Remsen/SACCBaseline.html.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Taxonomic note
Catharacta skua, C. lonnbergi, C. antarctica and C. maccormicki (Sibley and Monroe 1990, 1993), cross-regional species, are retained as separate species contra Christidis and Boles (1994) and Turbott (1990) who include lonnbergi and antarctica as subspecies of C. skua and AERC TAC (2003) who include C. maccormicki as a subspecies of C. skua. We accept the view in Chu et al. (2009) that Catharacta is best merged in Stercorarius.

Synonym(s)
Catharacta maccormicki Saunders, 1893, Stercorarius maccormicki AOU checklist (1998 + supplements), Stercorarius maccormicki SACC (2005), Stercorarius maccormicki Christidis and Boles (2008), Stercorarius maccormicki maccormicki AOU checklist (1998 + supplements), Stercorarius maccormicki maccormicki Christidis and Boles (2008)

Distribution and population
The South Polar Skua breeds throughout the Antarctic coast, especially in the Ross Sea rea. It undergoes a transequatorial migration, wintering as far north as Alaska (USA) and Greenland (to Denmark).

Population justification
The population is placed in the band 10,000-19,999 individuals, equating to 6,667-13,333 mature individuals, rounded here to 6,000-15,000 mature individuals.

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.

Ecology
The South Polar Skua breeds on relatively snow-free areas in Antartica (del Hoyo et al. 1992). It is usually reliant on fish (Pietz 1987), with predation on penguins being of variable importance (del Hoyo et al. 1992). It can, however, subside exclusively on penguins where a breeding colony is associated to a penguin rookery (Trillmich 1978, Young and Miller 1999). It is a trans-equatorial migrant, wintering in the North Pacific and North Atlantic (del Hoyo et al. 1992).

References
del Hoyo, J.; Elliot, A.; Sargatal, J. 1992. Handbook of the Birds of the World, vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain.

Trillmich, F. 1978. Feeding Territories And Breeding Success Of South Polar Skuas. Auk 95(1): 23-33.

Pietz, P. J. 1987. Feeding and nesting ecology of sympatric south polar and brown skuas. The Auk 104: 617-627.

Young, E. C., and Millar, C. D. 1999. Skua (Catharacta sp.) foraging behavior at the Cape Crozier Adélie Penguin (Pygoscelis adeliae) colony, Ross Island, Antarctica, and implications for breeding. Notornis 46: 287–297.

Further web sources of information
Hear sounds for this species from xeno-canto, the community database of shared bird sounds from around the world.

View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Butchart, S., Calvert, R., Ekstrom, J.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Stercorarius maccormicki. Downloaded from http://www.birdlife.org on 24/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species