Arctic tern  (Sterna paradisaea)

The Arctic tern is a long-distance migrant, making a staggering annual round-trip from its Arctic or northern temperate breeding range to the Antarctic where it spends winter (3). This is probably the longest migration undertaken by any bird (2) and means that the Arctic tern sees more sunlight each year than any other animal, as they experience a ‘second summer’ by travelling south in winter (5). They are very similar in appearance to the common tern (Sterna hirundo), so much so that birdwatchers call unidentified terns ‘commic terns’, an amalgamation of the two common names (6). Arctic terns are slightly smaller than common terns, and have a shorter bill and longer tail (2). The rump is white, the underparts are darker and the wing lacks the dark wedge on the outer edge, which is a key identifying feature of common terns (6) . During summer, the bill becomes bright red and lacks the black tip seen in common terns (2). Long tail streamers also develop in summer (2). A ‘kee-arr’ alarm call and a piping ‘pi-pi-pi-pi-pi’ call are produced (2) (6).

Arctic terns breed around the Arctic and temperate northern parts of the northern Hemisphere. They travel massive distances to overwinter in the Southern Ocean and Antarctica (4). The population that breeds in Britain and Ireland is at the southern-most limit of its breeding range. This range extends through Greenland and Iceland, along the Baltic and Scandinavian coasts reaching into Siberia. Most of the British breeding population occurs in Scotland, Orkney, Shetland and the Hebrides. Populations also occur in England in the northwest and northeast and there are small numbers in Norfolk and around the southern coast; they also breed in Anglesey in Wales (4).

In Britain, this species breeds around the coast (4) in open sand or shingle habitats or in moorland and coastal heathland (3). As they are vulnerable to predation, they often breed on offshore islands areas where there are no mammal predators such as rats and mink (3). In winter this species stays out at sea, resting on floating objects and ice (3).

The Arctic tern tends to arrive back in its breeding habitats after the long migration from May to June (3). Males court females with a ‘fish flight’, an impressive aerial display which culminates in the male presenting the female with a ‘gift’ in the form of a fish (6). Nesting tends to occur in a hollow on the ground at a good distance from the shore in short vegetation (4) (6). Pairs, which mate for life, produce between one and three eggs, which are incubated for up to 24 days (3) (6). After a further 24 days or so, the chicks will have fully fledged. The males defend the nests if they are threatened, by diving at potential predators and livestock (6).

Arctic terns are very long-lived species, with a maximum recorded life-span of 29 years (3). This species feeds mainly on fish, particularly sand eels (3) (4), which they catch by making short dives into the water (6). Feeding tends to occur within 3 km of the breeding colony, although they have been recorded to travel 10 km away in order to feed (4). When the breeding season is over, these birds head off once more on their long journey south (3).

This species is listed on the Birds of Conservation Concern Amber List; its population has experienced periodic declines since the 1980s and low breeding success throughout the 1990s (4). Declines have also occurred elsewhere in Europe. The main threats facing this species include nest predation by hedgehogs, introduced American mink (Mustela vison) and rats, as well as coastal development, disturbance by recreational activities, and a lack of the most important food source, sandeels, possibly caused by over-fishing by humans (4).

38% of the British breeding population occurs within Special Protection Areas (SPAs) and so the species receives a level of protection at these sites (4).

For more on British birds see the RSPB website:
http://www.rspb.org.uk

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk