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Aleutian Tern Onychoprion aleuticus

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)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: #http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls#.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
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.

Taxonomic note
Onychoprion aleuticus (del Hoyo and Collar 2014) was previously placed in the genus Sterna as S. aleutica.

Synonym(s)
Onychoprion aleuticus AOU checklist (1998 + supplements), Sterna aleutica Baird, 1869

Distribution and population
The Aleutian Tern breeds in the north Pacific Ocean on the coasts of Sakhalin and Kamchatka, Russia, on the Bering and Pacific coasts of Alaska (USA) and on the Aleutian Islands (USA). It is strongly migratory, wintering off Indonesia and Malaysia1.

Population justification
The global population is estimated to number c.30,000-35,000 individuals (Wetlands International 2006), while national population sizes have been estimated at c.50-1,000 individuals on migration in China and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Russia (Brazil 2009).

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

Ecology
This species is found over the waters of the Arctic and subarctic coastal plains. It feeds mainly on small fish which it catches by surface-dipping. Laying mainly occurs in June, usually in small monospecific colonies on a variety of habitats up to 20 km inland (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: Onychoprion aleuticus. Downloaded from http://www.birdlife.org on 22/09/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/09/2014.

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 Baird, 1869
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 223,000 km2
Country endemic? No
Links to further information
- Additional Information on this species