The Arctic tern, also known as the sea swallow, is a medium-sized, graceful seabird with long-pointed wings, a dagger-like bill, and long, deeply forked tail, similar to the common tern, but with shorter legs and bill. It spends most of its life in the air offshore, although during its long migration, it can be seen perched on driftwood and debris around coasts. It is a long-lived bird with many reaching up to 30 years of age, but may only breed once every three years.
Breeding birds: 53,000 pairs
Family: Gulls, Terns, And Skimmers
In breeding plumage, Arctic terns are pale grey with slightly paler underparts and a white rump, vent, and tail with long streamers. They have grey inner webs on the wings and a long narrow black line along the tips of the outer primaries.
On the head, the forehead and crown are black, and there is a small white patch on the cheeks. The bill is deep red, the eyes are dark brown, and the legs, and webbed feet are red. Males and females look similar.
Outside of breeding season, Arctic terns have a white forehead and black bill, legs, and feet.
Juveniles have darker upperparts and brown-tipped feathers on the mantle and inner wings. The head is similar to the adult in non-breeding plumage, and they have pink bills, legs and feet with some black patches.
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Arctic terns start breeding in May and produce 1 brood a season. They are monogamous and mate for life, and nest in scattered colonies which are defended by the males. They breed near rivers, or on beaches, heath, and islands, returning to the same breeding grounds each year. The nest is situated in a shallow scrape in the ground which may be lined with moss or grasses, among short vegetation, sand, or gravel away from water.
Arctic terns lay 1-3 smooth, buff, or pale olive eggs with darker spots and scribbles that camouflage them well against the ground, and which are incubated by the male and female for 20-25 days. Chicks have brown or grey upperparts with dark markings, and white underparts with a grey chin. Both parents care for the chicks and although they can move in the first couple of days, they are brooded for 10 days, and fledge at about 21 days. They undertake their first migration accompanied by their parents and reach sexual maturity at 4 years.
Arctic terns feed mainly on small fish, in particularly sand eels but will also eat crustaceans, molluscs, and insects.
On land they will feed on caterpillars and worms, and occasionally berries in early spring.
Breeding Arctic terns can be found in Northern England, Scotland and north Wales mainly on islands such as the Farne Islands or the Northern Isles. During the spring passage they can also be seen on inland reservoirs.
European visitors start to arrive back from the Antarctic in May with northernmost birds getting back in June. They will start their migration south in late July and August.
Arctic terns make the longest migrations of any bird travelling about 70 km a year which adds up to an impressive 2.4 million km over its lifetime.
