Species

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). 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 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)
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.
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
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.
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.
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
SACC. 2006. A classification of the bird species of South America. Available at: http://www.museum.lsu.edu/~Remsen/SACCBaseline.html.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

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
The Arctic Tern has a circumpolar range, breeding in the Arctic and subarctic regions of Europe, Asia and North America as far south as Brittany, France and Massachusetts (USA). It is a transequatorial migrant, and can be found wintering throughout the Southern Ocean to the edge of the Antarctic ice and the southern tips of South America and Africa (del Hoyo et al. 1996). Overall population trends are relatively unknown, though the 2008 breeding season in the north of the United Kingdom was reported to be a failure by the RSPB.

Population justification
The global population is estimated to number > c.2,000,000 individuals (Wetlands International 2006), while the population in Russia has been estimated at c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration (Brazil 2009).

Trend justification
The overall population trend is decreasing, although some populations have unknown trends (Wetlands International 2006).

Ecology
Behaviour The species is a very strong migrant and makes exceptional long-distance movements offshore or along western continental coastlines (del Hoyo et al. 1996, Melville and Shortridge 2006) between its high Arctic breeding grounds and Antarctic wintering grounds (del Hoyo et al. 1996). It breeds between May and July (although the exact timing varies with temperature and food availability) in solitary pairs or colonies of a few to several hundred pairs (usually 2-25) (del Hoyo et al. 1996), and remains gregarious throughout the year especially when roosting, foraging (Snow and Perrins 1998) and on passage (Higgins and Davies 1996). The species generally feeds within 3 km of breeding colonies but may occasionally forage up to 50 km away (del Hoyo et al. 1996). On its wintering grounds in Antarctica it may also forage in association with Antarctic Minke Whale Balaenoptera bonaerensis in the open ocean north of the pack-ice zone (Higgins and Davies 1996). Habitat Breeding The species breeds along northern coastlines (del Hoyo et al. 1996)and on inshore islands (Flint et al. 1984, Snow and Perrins 1998) as well as inland on tundra and forest-tundra (Flint et al. 1984). It shows a preference for habitats with a vegetation cover of less than 40 %, nesting on sand or shingle beaches, ridges (del Hoyo et al. 1996) and spits (Flint et al. 1984), rocky ground (Flint et al. 1984, Richards 1990, del Hoyo et al. 1996) and small islands (Flint et al. 1984, del Hoyo et al. 1996, Snow and Perrins 1998) in lakes and coastal lagoons (del Hoyo et al. 1996). It may also nest on islets or banks along rivers (Snow and Perrins 1998), on swampy tundra (Flint et al. 1984, del Hoyo et al. 1996) and peatlands with bog hummocks (del Hoyo et al. 1996) and reed-covered flats (Flint et al. 1984), or on inland heaths, rough pastures (del Hoyo et al. 1996, Snow and Perrins 1998), meadows (del Hoyo et al. 1996) and sedge grassland (Snow and Perrins 1998) not far from water (Flint et al. 1984). The species also forages offshore, in ice-filled coastal bays or over wet tundra (del Hoyo et al. 1996). Non-breeding On passage it largely flies over open ocean (Snow and Perrins 1998) resting at sea on kelp, logs or flotsam, but may occur inland or along coastlines on beaches, reefs and spits (Higgins and Davies 1996). During the winter the species is pelagic, foraging at the edges of pack-ice, icebergs and ice-floes near shore (especially in channels between ice-floes) (Higgins and Davies 1996) and up to 24 km offshore (Higgins and Davies 1996, del Hoyo et al. 1996) often in association with Antarctic Minke Whale Balaenoptera bonaerensis (Higgins and Davies 1996). It also roosts on ice-floes and icebergs during this season (Higgins and Davies 1996). Diet Its diet consists predominantly of fishas well as crustaceans (especially planktonic species), molluscs, insects (e.g. caterpillars, Chironomidae) and earthworms (del Hoyo et al. 1996). It will also take berries in the early spring on arrival on its breeding grounds but does not readily switch to other prey items when preferred prey supplies fail (del Hoyo et al. 1996). Breeding site The nest is a shallow scrape (del Hoyo et al. 1996) in sand, shingle or turf (Richards 1990) on beaches, ridges (del Hoyo et al. 1996) and spits (Flint et al. 1984), rocky ground (Flint et al. 1984, Richards 1990, del Hoyo et al. 1996), small islands (Flint et al. 1984, del Hoyo et al. 1996, Snow and Perrins 1998) in lakes, coastal lagoons (del Hoyo et al. 1996) and rivers (Snow and Perrins 1998), swampy tundra (Flint et al. 1984, del Hoyo et al. 1996) and peatlands with bog hummocks (del Hoyo et al. 1996) and reed-covered flats (Flint et al. 1984), or on inland heaths, rough pastures (del Hoyo et al. 1996, Snow and Perrins 1998), meadows (del Hoyo et al. 1996) and sedge grassland (Snow and Perrins 1998) not far from water (Flint et al. 1984). It will also nest on artificial structures (del Hoyo et al. 1996). Management information Removing feral American mink Neovison vison from a large archipelago with many small islands in the Baltic Sea resulted in an increase in the breeding density of this species in the area (Nordstrom et al. 2003). Gull control measures may also be practised successfully at some sites to reduce predation and displacement, especially when carried out in conjunction with the use of recordings and models to induce recolonistion of nesting terns (Buckley and Buckley 1984).

Threats
The species is potentially threatened by climate change because it has a geographically bounded distribution: its global distribution is restricted to within c.10^o latitude from the polar edge of continent and within which 20-50% of current vegetation type is projected to disappear under doubling of CO2 levels (Birdlife International, unpublished data).

Related state of the world's birds case studies

• Migrating birds know no boundaries

References
Flint, V. E.; Boehme, R. L.; Kostin, Y. V.; Kuznetsov, A. A. 1984. A field guide to birds of the USSR. Princeton University Press, Princeton, New Jersey.

Buckley, P. A.; Buckley, F. G. 1984. Seabirds of the north and middle Atlantic coasts of the United States: their status and conservation. In: Croxall, J.P.; Evans, P.G.H.; Schreiber, R.W. (ed.), Status and conservation of the world's seabirds, pp. 101-133. International Council for Bird Preservation, Cambridge, U.K.

Richards, A. 1990. Seabirds of the northern hemisphere. Dragon's World Ltd, Limpsfield, U.K.

Higgins, P. J.; Davies, S. J. J. F. 1996. Handbook of Australian, New Zealand and Antarctic birds vol 3: snipe to pigeons. Oxford University Press, Oxford.

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

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

Melville, D. S.; Shortridge, K. F. 2006. Migratory waterbirds and avian influenza in the East Asian-Australasian Flyway with particular reference to the 2003-2004 H5N1 outbreak. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 432-438. The Stationary Office, Edinburgh, UK.

Nordström, M.; Högmander, J.; Nummelin, J.; Laine, J.; Laanetu, N.; Korpimäki, E. 2003. Effects of feral mink removal on seabirds, waders and passerines on small islands in the Baltic Sea. Biological Conservation 109: 359-368.

Further web sources of information
Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

Hear sounds for this species from xeno-canto, the community database of shared bird sounds from around the world.

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

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

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

Recommended citation
BirdLife International (2013) Species factsheet: Sterna paradisaea. Downloaded from http://www.birdlife.org on 22/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2013.

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

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