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)
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

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 lonnbergi Mathews, 1912, Stercorarius antarcticus Christidis and Boles (2008), Stercorarius antarcticus antarcticus Christidis and Boles (2008)

Distribution and population
The Brown Skua is found on the Antarctic Peninsula and subantarctic islands of the Atlantic, Indian and Pacific Oceans, wintering near or slightly dispersed from the breeding area (del Hoyo et al. 1996).

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
This marine species is found on or around subantarctic islands populated by burrow-nesting seabirds or penguins. It is highly predatory, feeding mainly on other birds but will also scavenge around fishing boats and ships and feed at sea. Breeding begins in October and November. Birds are loosely colonial but highly territorial, nesting on grass, gravel or bare rock. Individuals at some northern colonies are resident throughout the year, but will disperse over the sea where conditions are harsher (del Hoyo et al. 1996).

References
del Hoyo, J.; Elliott, A.; Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

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 lonnbergi. Downloaded from http://www.birdlife.org on 22/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2013.

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.

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Additional resources for this species

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