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Antarctic Tern Sterna vittata

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 is unknown, but is not believed to be declining sufficiently rapidly to 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)
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
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 Antarctic Tern can be found breeding on a large number of islands in the Southern Oceans and off the coast of Antarctica. Some birds from the south of its range have been found wintering on the coast of Argentina and South Africa1.

Population justification




Trend justification
The population of S. v. sanctipauli is decreasing, but trends for the remainder of populations, and therefore the overall trend, is unknown (Wetlands International 2006).

Ecology
Behaviour Breeding populations in the southern part of this species's range are migratory, post-breeding flocks migrating long distances to winter off the southern coasts of South America and South Africa (del Hoyo et al. 1996). Those populations that winter in South America arrive from mid April and depart again from mid-October, during which time the adults moult their flight feathers (del Hoyo et al. 1996). Some populations around Antarctica remain close to their breeding grounds all year round however and moult on ice-floes or icebergs on open water (del Hoyo et al. 1996). The species breeds between November and December although the exact timing varies depending on climate and food availability (del Hoyo et al. 1996). It usually nests in small loose colonies of 5-20 pairs although it may often nest singly and has been known to nest in larger colonies of up to 1,000 pairs (del Hoyo et al. 1996). It forages in inshore waters singly or in small flocks (Urban et al. 1986, del Hoyo et al. 1996) and in the winter communal roosts of 10-1,200 individuals often form (Urban et al. 1986). Habitat Breeding The species breeds on rocky areas very near the coast or a short distance inland (Higgins and Davies 1996), showing a strong preference for nesting sites that are inaccessible to ground predators (del Hoyo et al. 1996). Suitable nesting habitats include vegetated or unvegetated rocky islets, offshore stacks, coastal cliffs, gravel, rocky and sandy beaches and sparse scrubland (del Hoyo et al. 1996). The species forages in inshore waters up to 200 m from the shore and in coves, bays, inlets, harbours and off estuaries, especially where there are large forests of kelp (Higgins and Davies 1996). Non-breeding Outside of the breeding season the species moves to the nearest area of open water or to pelagic zones far from land (Higgins and Davies 1996) where it forms communal roosts on ice-floes and icebergs (Higgins and Davies 1996) and forages in patches of unfrozen inshore water or in open water along the edge of ice. More migratory populations also winter off the temperate southern coasts of South America and South Africa with adjacent cold water currents (Higgins and Davies 1996), inhabiting rocky headlands and beaches (del Hoyo et al. 1996). Diet Its diet consists predominantly of small fish although it also takes polychaetes (del Hoyo et al. 1996), molluscs (Higgins and Davies 1996) (e.g. limpets) (del Hoyo et al. 1996), crustaceans (e.g. euphausiids and amphipods), insects (del Hoyo et al. 1996) and algae (Higgins and Davies 1996). Breeding site The species nests in natural depressions in rock or in shallow scrapes in soil, sand or vegetation (del Hoyo et al. 1996) that may be positioned on ledges or crevices of sheer cliffs, boulders at the base of cliffs, headlands, stacks, rocky islets, ridges, spits and peninsulas, rock fields by freshwater, and beaches of gravel, coarse shingle and sand (Higgins and Davies 1996).

Threats
The species is vulnerable to human disturbance and to the introduction of ground-based predators on offshore islands including domestic or feral cats Felis catus (del Hoyo et al. 1996, Hockey et al. 2005) and rats (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.

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.

Hockey, P. A. R.; Dean, W. R. J.; Ryan, P. G. 2005. Roberts birds of southern Africa. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa.

Urban, E. K.; Fry, C. H.; Keith, S. 1986. The birds of Africa vol. II. Academic Press, London.

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

Recommended citation
BirdLife International (2014) Species factsheet: Sterna vittata. Downloaded from http://www.birdlife.org on 11/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 11/07/2014.

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.

Additional resources for this species

ARKive species - Antarctic tern (Sterna vittata) 0

Key facts
Current IUCN Red List category Least Concern
Family Laridae (Gulls and terns)
Species name author Gmelin, 1789
Population size mature individuals
Population trend Unknown
Distribution size (breeding/resident) 485,000 km2
Country endemic? No
Links to further information
- Additional Information on this species