Tern

Tern, common name for a number of seabirds in the same family as gulls. They are found around the world, the majority of them in tropical and subtropical regions. Many migrate long distances; the best known is the arctic tern, which nests in the far north and migrates to the Antarctic region in the autumn.

Most terns are white, gray, and black; some species have brightly colored bills and feet. They range in length from 20 to 51 cm (8 to 20 in), with short legs and long, narrow wings. Most species have forked tails and straight, sharp bills. The largest, the Caspian tern, is 51 cm (20 in) long and has a wingspan of 135 cm (53 in). The smallest is the least tern, which is 20 cm (8 in) long and has a wingspan of 51 cm (20 in). Most terns inhabit ocean coasts, where they feed on fish and small marine invertebrates. Forster's tern of North America nests in prairie marshes as well as on coasts. Members of the genus known collectively as marsh terns are confined to freshwater areas and feed primarily on insects. Best known of these is the black tern of North America and Europe.

Most terns nest on the ground in dense colonies in open areas such as beach or tundra; nests vary from a simple depression to an elaborate structure of twigs, grass, and bits of shell. The noddies, a genus of dark-colored tropical terns, nest in trees or on cliff ledges. The white, or fairy, tern, which inhabits tropical islands around the world, incubates its single egg on a bare branch or in the crotch of a tree, with no nest. Tropical terns rarely lay more than one egg, but northern species such as the common tern and the roseate tern often lay three and occasionally four eggs.

Terns are long-lived. Individuals continuing to breed at well over 20 years of age have been documented in several species. Most do not breed until they are three years old, although they may return to their natal colonies earlier. The sooty tern, which inhabits tropical islands, comes to land only to breed, and its plumage is not waterproof. Young birds thus spend as much as three years in the air (unless they can find floating objects on which to sit) until they are of breeding age.

Scientific classification: Terns belong to the subfamily Sterninae in the family Laridae, order Charadriiformes. The arctic tern is classified as Sterna paradisaea, the Caspian tern as Sterna caspia, the least tern as Sterna antillarum, and Forster's tern as Sterna forsteri. Marsh terns make up the genus Chlidonias. The black tern is classified as Chlidonias niger. Noddies make up the genus Anous. The white, or fairy, tern is classified as Cygis alba, the common tern as Sterna hirundo, the roseate tern as Sterna dougallii, and the sooty tern as Sterna fuscata.

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