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LC
Forster's Tern Sterna forsteri

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 appears to be increasing, 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 very 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)
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.
SACC. 2006. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.html#.

Distribution and population
Forster's Tern can be found in North and Central America, breeding seasonally in southern Canada and northern USA, wintering in south-east and coastal south-western USA, along the eastern and western coast of Mexico and in Central America. It can also be found year-round on the Atlantic coast of the USA from Virginia to Texas (del Hoyo et al. 1996).

Trend justification
This species has undergone a small or statistically insignificant increase over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Ecology
This species breeds mainly at freshwater lakes, potholes, inland and coastal marshes and salt-pold dykes, and rarely on sand, mud or rocky islets. It feeds over lakes, streams and estuaries favouring water less than 1 m deep. It feeds mainly on small fish (5-7 cm), but also aquatic insects and crustaceans. The exact composition of its diet and prey species varies depending on locality. It feeds mainly by plunge-diving or dipping from the surface, and occaisionally diving from a perch in a kingfisher-like fashion. It has been seen to maintain a breeding territory. Breeding occurs between April and May on the Gulf Coast and to late May elsewhere, forming loose colonies of 5-250 pairs, though is sometimes solitary. It prefers nesting among floating and emergent vegetations, but will also nest on boards, dredge spoil, sand or fine shell and on coarse gravel islands (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.

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: Sterna forsteri. Downloaded from http://www.birdlife.org on 23/11/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/11/2014.

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.

Additional resources for this species

ARKive species - Forster's tern (Sterna forsteri) 0

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls, Terns, Skimmers)
Species name author Nuttall, 1834
Population size mature individuals
Population trend Increasing
Distribution size (breeding/resident) 1,800,000 km2
Country endemic? No
Links to further information
- Additional Information on this species