LC
Brown Skua Catharacta antarctica



Justification

Justification of Red List Category
This species has an extremely 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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to 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.

Population justification
The total population has been estimated to number c.13,000-14,000 pairs (del Hoyo et al. 1996), assumed to equate to 26,000-28,000 mature individuals, or 39,000-42,000 individuals in total.

Trend justification
The largest known colony of the nominate race, C. antarctica antarctica, has undergone a 47% decline in the last 5 years, as such the species is suspected to be in decline, but the overall magnitude of decline is uncertain.

Distribution and population

Catharacta antarctica 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).

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 (del Hoyo et al. 1996).

Threats

The largest known colony of the nominate race, C. antarctica antarctica, has undergone a 47% decline in the last 5 years. The causes are largely unknown, but may be related to nest predation, kleptoparasitism and competition for prey, primarily the Thin-billed Prion Pachyptila belcheri, all performed by the Striated Caracara Phalcoboenus australis, the population of which has been increasing over the same period. 

Acknowledgements

Text account compilers
Ekstrom, J., Bennett, S., Butchart, S., Martin, R., Calvert, R., Stuart, A., Symes, A., Taylor, J.


Recommended citation
BirdLife International (2019) Species factsheet: Catharacta antarctica. Downloaded from http://www.birdlife.org on 20/05/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/05/2019.