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.

Family/Sub-family Laridae

Species name author Pontoppidan, 1763

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Christidis and Boles (1994), Christidis and Boles (2008), Cramp and Simmons (1977-1994), Dowsett and Forbes-Watson (1993), SACC (2005 + updates), Sibley and Monroe (1990, 1993), Stotz et al. (1996), Turbott (1990)

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.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

2,000,000

unset

-

No

Range & 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 Africa¹. 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.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour The species is a very strong migrant and makes exceptional long-distance movements offshore or along western continental coastlines^{1, 6} between its high Arctic breeding grounds and Antarctic wintering grounds¹. 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)¹, and remains gregarious throughout the year especially when roosting, foraging⁴ and on passage⁵. The species generally feeds within 3 km of breeding colonies but may occasionally forage up to 50 km away¹. 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 zone⁵. Habitat Breeding The species breeds along northern coastlines¹ and on inshore islands^{3, 4} as well as inland on tundra and forest-tundra³. It shows a preference for habitats with a vegetation cover of less than 40 %, nesting on sand or shingle beaches, ridges¹ and spits³, rocky ground^{1, 2, 3} and small islands^{1, 3, 4} in lakes and coastal lagoons¹. It may also nest on islets or banks along rivers⁴, on swampy tundra^{1, 3} and peatlands with bog hummocks¹ and reed-covered flats³, or on inland heaths, rough pastures^{1, 4}, meadows¹ and sedge grassland⁴ not far from water³. The species also forages offshore, in ice-filled coastal bays or over wet tundra¹. Non-breeding On passage it largely flies over open ocean⁴ resting at sea on kelp, logs or flotsam, but may occur inland or along coastlines on beaches, reefs and spits⁵. 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)⁵ and up to 24 km offshore^{1, 5} often in association with Antarctic Minke Whale Balaenoptera bonaerensis⁵. It also roosts on ice-floes and icebergs during this season⁵. Diet Its diet consists predominantly of fish as well as crustaceans (especially planktonic species), molluscs, insects (e.g. caterpillars, Chironomidae) and earthworms¹. 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 fail¹. Breeding site The nest is a shallow scrape¹ in sand, shingle or turf² on beaches, ridges¹ and spits³, rocky ground^{1, 2, 3}, small islands^{1, 3, 4} in lakes, coastal lagoons¹ and rivers⁴, swampy tundra^{1, 3} and peatlands with bog hummocks¹ and reed-covered flats³, or on inland heaths, rough pastures^{1, 4}, meadows¹ and sedge grassland⁴ not far from water³. It will also nest on artificial structures¹. 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 area⁸. 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 terns⁷.

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 levels⁹.

References 1. del Hoyo et al. (1996). 2. Richards (1990). 3. Flint et al. (1984). 4. Snow and Perrins (1998). 5. Higgins and Davies (1996). 6. Melville and Shortridge (2006). 7. Buckley and Buckley (1984). 8. Nordstrom et al. (2003). 9. Birdlife International, unpublished data

Further web sources of information

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

Text account compilers Stuart Butchart (BirdLife International), Rob Calvert (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International), Rob Calvert (BirdLife International)

Recommended citation BirdLife International (2010) Species factsheet: Sterna paradisaea. Downloaded from http://www.birdlife.org on 30/7/2010

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