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LC
Black-tailed Gull Larus crassirostris

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 is extremely large, and hence does not 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.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Distribution and population
The Black-tailed Gull is found in east Asia, specifically the coasts of eastern China, Japan, North Korea, South Korea and Sakhalin, Russia1.

Population justification
The global population is estimated to number > c.1,100,000 individuals (Wetlands International 2006), while national population estimates include: c.100-100,000 breeding pairs and c.50-10,000 wintering individuals in China; c.50-1,000 wintering individuals, c.1,000-10,000 individuals on migration and < c.100 breeding pairs in Taiwan; c.10,000-100,000 breeding pairs in Korea; c.10,000-100,000 breeding pairs in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).

Trend justification
Although Wetlands International consider the current population trend to be unknown, it is suspected to be stable in the absence of evidence for any declines or substantial threats (del Hoyo et al. 1996).

Ecology
This species is found on coasts, and in bays and estuaries. Its diet varies locally and annually, but includes small fish, crustaceans, insects, offal, molluscs and polychaetes. It often follows fishing boats and can be a kleptoparasite. Colonies form mid-April on sandy or rocky seashores, sea cliffs and rocky islets. Many colonies hold over 10,000 pairs. Post-breeding it moves to areas rich in food (del Hoyo et al. 1996).

References
Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

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

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Further web sources of information
Explore HBW Alive for further information on this species

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

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

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

Recommended citation
BirdLife International (2014) Species factsheet: Larus crassirostris. Downloaded from http://www.birdlife.org on 23/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/08/2014.

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.

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls, Terns, Skimmers)
Species name author Vieillot, 1818
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 157,000 km2
Country endemic? No
Links to further information
- Additional Information on this species