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LC
Black-naped Tern Sterna sumatrana

Justification
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). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, 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. 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
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Taxonomic note
The BirdLife Taxonomic Working Group is aware that phylogenetic analyses have been published which have proposed generic rearrangements which may affect this species, but prefers to wait until work by other taxonomists reveals how these changes affect the entire groups involved.

Distribution and population
This species ranges in tropical and subtropical areas of the Indian Ocean and western Pacific Ocean. In the western Indian Ocean it breeds on the Aldabra and Amirante Islands, Seychelles, Chagos Islands (British Indian Ocean Territory) and the Maldives and can be found on the eastern African coast. Its range in the eastern Indian Ocean and Pacific ecompasses the Andaman Islands, India, east to southern Japan and China, south through Indonesia, Malaysia, the Philippenes and New Guinea to north-east Australia and some islands in the western-central Pacific (del Hoyo et al. 1996).

Population justification
The global population size has not been quantified, though national population estimates include: c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in China; c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Taiwan and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Japan (Brazil 2009).

Trend justification
The population trend is difficult to determine because of uncertainty over the extent of threats to the species (del Hoyo et al. 1996).

Ecology
This species frequents small offshore islands, reeds, sand spits and rocky cays, feeding in atoll lagoons and close inshore over breakers, but sometimes also at sea. It feeds mainly on small fish and will almost always forage singly by shallow plunge-diving or surface-diving. Its breeding season varies depending on locality, usually forming small colonies of 5 to 20 pairs, but sometimes up to 200 pairs. Colonies are often monospecific and formed on unlined depression in the sand or in gravel pockets on coral banks close to the high tide line (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.

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

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

Recommended citation
BirdLife International (2014) Species factsheet: Sterna sumatrana. Downloaded from http://www.birdlife.org on 13/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/07/2014.

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 and terns)
Species name author Raffles, 1822
Population size Unknown mature individuals
Population trend Unknown
Distribution size (breeding/resident) 4,250,000 km2
Country endemic? No
Links to further information
- Additional Information on this species