Terns

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Terns

Biology of terns

Terns of north america

Conservation of terns

Resources

Terns are fast-flying coastal birds in the family Sternidae, which includes some 44 species. Most species of terns are found in the tropics and subtropics, but these birds occur on all continents. They range from the limits of land in the highest Arctic, to the fringes of Antarctica. Most terns breed and occur in coastal marine environments, or in the vicinity of inland lakes, rivers, and marshes.

Biology of terns

Terns are slender birds with long, pointed wings, and are adept fliers. Their tail is usually forked to some degree, and their bill is sharply pointed. The usual coloration is some combination of white, gray, and/or black.

The smallest species is the little tern (Sterna albifrons ), which is only 9 in (23 cm) in body length and 1.8 oz (50 g) in weight. The largest species is the Caspian tern (Hydroprogne caspia ), which is 20 in (50 cm) long, and weighs 25 oz (700 g).

Most terns feed on fish, small squid, or large invertebrates. Species occurring in freshwater habitats may also eat amphibians and large insects. Terns typically hunt their aquatic prey by plunging head-first into water, often after having located their quarry by briefly hovering.

Terns typically nest in colonies, some of which are large. The usual nesting locale is a gravel shore, generally on an island or relatively isolated peninsula. The typical nest built by terns is a simple scrape, but

tropical terns known as noddies (Anous spp.) build a more substantial nest in a tree or on cliff ledges. Some fairy terns do not build a nest at allthey lay a single egg, wedged into the fork between two branches of a tree.

Terns of north america

Fourteen species of terns breed regularly in North America. The most abundant species is the common tern (Sterna hirundo ), which also breeds widely in Eurasia. The breeding range of this species is from the subarctic, to the Great Lakes and temperate regions of the Atlantic coast. The common tern winters from southern parts of coastal North America through to southern South America. This tern has a black cap, a gray mantle (the back of the wings), a white breast, and a red beak with a blackish tip.

The arctic tern (S. paradisaea ) is an abundant species that breeds from subarctic regions to the very limit of land in the Arctic of North America and Eurasia. It winters in the waters of the Southern Ocean. The arctic tern undertakes extraordinarily long migrations between its breeding and wintering habitats, with some populations traversing a distance of more than 22,000 mi (36,000 km) each year. Because it spends so much time in high latitudes of both hemispheres, where day length is long during the summer, the arctic tern may see more hours of daylight each year than any other creature. The arctic tern has similar coloration to the common tern, but it has an allred beak and shorter, red legs.

Forsters tern (S. forsteri ) breeds in salt and freshwater marshes of the northern prairies, and to a lesser degree along the southern coasts of the Pacific and Atlantic Oceans. The roseate tern (S. dougallii ) is locally common along the Atlantic coast of the eastern United States and as far north as Nova Scotia. The roseate tern also breeds in coastal places in western Europe, the West Indies, Venezuela, Africa, the Indian Ocean, south and Southeast Asia, Australia, and many South Pacific islands.

The royal tern (Thalasseus maximus ) is a relatively large, crested species that breeds on the Atlantic and Pacific coasts of North America, and also in Eurasia. This species winters on the coasts of south Florida, the Gulf of Mexico, and parts of the Caribbean.

The Caspian tern is the largest species of tern. This species breeds on large lakes and rivers and at a few places along the subarctic seacoast of North America. The Caspian tern is a wide-ranging species, also breeding in Eurasia, Africa, Australia, and New Zealand. This species winters along the coasts of southern California, Baja California, the Gulf of Mexico, and Caribbean islands.

The black tern (Chlidonias niger ) is a dark-gray locally abundant species breeding on lakes and freshwater marshes in both North America and Eurasia. North American birds winter in Central America and northern South America. The sooty tern (Sterna fuscata ) and noddy tern (Anous stolidas ) only breed in the Dry Tortugas, small U.S. islands south of west Florida.

Conservation of terns

During the nineteenth century, many species of terns were rapaciously hunted for their plumage, which was valuable at the time for decorating the clothing of fashionable ladies. Sometimes, an artistic statement was made by mounting an entire, stuffed tern onto a broad-brimmed, ladys hat. Fortunately, the plumage of terms or other birds is not much used for these purposes any more.

In many places, terns have been deprived of important nesting habitat, as beaches and other coastal places have been appropriated and developed for use by humans. Frequent disturbances by pedestrians, all-terrain vehicles, boats, and other agents also disrupt the breeding of terns, usually by causing brooding adults to fly, which exposes their eggs or young to predation by other birds, especially gulls.

In many parts of their breeding range, tern eggs and chicks are taken by a number of the larger species of gulls (Larus spp.). The populations of many gull species have increased enormously in most of the world, because these birds have benefited greatly from the availability of fish waste discarded by fishing boats and processing plants, and from other foods available at garbage dumps. Gulls are highly opportunistic feeders, and will predate tern chicks, and sometimes adults, whenever it is easy to do so. The negative effects of gulls on terns are an important, indirect consequence of the fact that gulls have benefited so tremendously from the activities of humans.

Some species of terns are threatened, especially the black-fronted tern (Chlidonias albostriatus ) of New Zealand, the Chinese crested-tern (S. bernsteini ) of Southeast Asia, and the Peruvian tern (S. lorata ) of Chile, Ecuador, and Peru.

See also Gulls; Migration.

Resources

BOOKS

del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World. Vol. 3, Hoatzin to Auks. Barcelona: Lynx Edicions, 1996.

Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.

Hay, J. The Bird of Light. New York: Norton, 1991.

Olsen, K.M., and H. Larsson. Terns of Europe and North America. Princeton, NJ: Princeton University Press, 1995.

Bill Freedman

views updated

Terns

Terns are fast-flying coastal birds in the family Sternidae, which includes some 42 species . Most species of terns are found in the tropics and subtropics, but these birds occur on all continents. They range from the limits of land in the highest Arctic, to the fringes of Antarctica . Most terns breed and occur in coastal marine environments, or in the vicinity of inland lakes, rivers , and marshes.


Biology of terns

Terns are slender birds with long, pointed wings, and are adept fliers. Their tail is usually forked to some degree, and their bill is sharply pointed. The usual coloration is some combination of white, gray, and/or black.

The smallest species is the little tern (Sterna albifrons), which is only 9 in (23 cm) in body length and 1.8 oz (50 g) in weight. The largest species is the Caspian tern (Hydroprogne caspia), which is 20 in (50 cm) long, and weighs 25 oz (700 g).

Most terns feed on fish , small squid , or large invertebrates . Species occurring in freshwater habitats may also eat amphibians and large insects . Terns typically hunt their aquatic prey by plunging head-first into water , often after having located their quarry by briefly hovering.

Terns typically nest in colonies, some of which are large. The usual nesting locale is a gravel shore, generally on an island or relatively isolated peninsula . The typical nest built by terns is a simple scrape, but tropical terns known as noddies (Anous spp.) build a more substantial nest in a tree or on cliff ledges. Some fairy terns do not build a nest at all—they lay a single egg, wedged into the fork between two branches of a tree.


Terns of North America

Fourteen species of terns breed regularly in North America . The most abundant species is the common tern (Sterna hirundo), which also breeds widely in Eurasia. The breeding range of this species is from the subarctic, to the Great Lakes and temperate regions of the Atlantic coast. The common tern winters from southern parts of coastal North America through to southern South America . This tern has a black cap, a grey mantle (the back of the wings), a white breast, and a red beak with a blackish tip.

The arctic tern (S. paradisaea) is an abundant species that breeds from subarctic regions to the very limit of land in the Arctic of North America and Eurasia. It winters in the waters of the Southern Ocean. The arctic tern undertakes extraordinarily long migrations between its breeding and wintering habitats, with some populations traversing a distance of more than 22,000 mi (36,000 km) each year. Because it spends so much time in high latitudes of both hemispheres, where day length is long during the summer, the arctic tern may see more hours of daylight each year than any other creature. The arctic tern has similar coloration to the common tern, but it has an all-red beak and shorter, red legs.

Forster's tern (S. forsteri) breeds in salt and freshwater marshes of the northern prairies, and to a lesser degree along the southern coasts of the Pacific and Atlantic Oceans. The roseate tern (S. dougallii) is locally common along the Atlantic coast of the eastern United States and as far north as Nova Scotia. The roseate tern also breeds in coastal places in western Europe , the West Indies, Venezuela, Africa , the Indian Ocean, south and southeast Asia , Australia , and many south Pacific islands.

The royal tern (Thalasseus maximus) is a relatively large, crested species that breeds on the Atlantic and Pacific coasts of North America, and also in Eurasia. This species winters on the coasts of south Florida, the Gulf of Mexico, and parts of the Caribbean.

The Caspian tern is the largest species of tern. This species breeds on large lakes and rivers and at a few places along the subarctic seacoast of North America. The Caspian tern is a wide-ranging species, also breeding in Eurasia, Africa, Australia, and New Zealand. This species winters along the coasts of southern California, Baha California, the Gulf of Mexico, and Caribbean islands.

The black tern (Chlidonias niger) is a dark-grey locally abundant species breeding on lakes and freshwater marshes in both North America and Eurasia. North American birds winter in Central America and northern South America. The sooty tern (S. fuscata) and noddy tern (Anous stolidas) only breed in the Dry Tortugas, small U.S. islands south of West Florida.


Conservation of terns

During the nineteenth century, many species of terns were rapaciously hunted for their plumage, which was valuable at the time for decorating the clothing of fashionable ladies. Sometimes, an artistic statement was made by mounting an entire, stuffed tern onto a broad-brimmed, lady's hat. Fortunately, the plumage of terms or other birds is not much used for these purposes any more.

In many places, terns have been deprived of important nesting habitat , as beaches and other coastal places have been appropriated and developed for use by humans. Frequent disturbances by pedestrians, all-terrain vehicles, boats, and other agents also disrupt the breeding of terns, usually by causing brooding adults to fly, which exposes their eggs or young to predation by other birds, especially gulls .

In many parts of their breeding range, tern eggs and chicks are taken by a number of the larger species of gulls (Larus spp.). The populations of many gull species have increased enormously in most of the world, because these birds have benefited greatly from the availability of fish waste discarded by fishing boats and processing plants, and from other foods available at garbage dumps. Gulls are highly opportunistic feeders, and will predate tern chicks, and sometimes adults, whenever it is easy to do so. The negative effects of gulls on terns are an important, indirect consequence of the fact that gulls have benefited so tremendously from the activities of humans.

Some species of terns are threatened, such as the black-fronted tern (Chlidonias albostriatus) of New Zealand, the black-bellied tern (Sterna acuticauda) of South and Southeast Asia, the Chinese crested-tern (S. bernsteini) of Southeast Asia, the fairy tern (S. nereis) of Australia, and the Kerguelen tern (S. virgata) of southern Africa.

See also Gulls; Migration.

Resources

books

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.

Hay, J. The Bird of Light. New York: Norton, 1991.


Bill Freedman

views updated

tern1 / tərn/ • n. a seabird (Sterna and other genera, family Sternidae, or Laridae) related to the gulls, typically smaller and more slender, with long pointed wings and a forked tail. tern2 • n. rare a set of three, esp. three lottery numbers that when drawn together win a large prize.

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ternadjourn, astern, Berne, burn, churn, concern, discern, earn, fern, fohn, kern, learn, Lucerne, quern, Sauternes, spurn, stern, Sterne, tern, terne, Traherne, turn, urn, Verne, yearn •Bayern • Blackburn • heartburn •Hepburn • Raeburn • Swinburne •Gisborne, Lisburn •sideburn • sunburn • Bannockburn •lady-fern • Vättern • extern •cittern, gittern •Comintern • taciturn •nocturn, nocturne •U-turn • upturn

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tern (sea swallow) Any of several species of graceful seabirds that live throughout the world. The tern is usually white and grey, and has a pointed bill, long pointed wings, a forked tail and webbed feet; it dives for fish and crustaceans. Length: to 55cm (22in). Family Laridae; genus Sterna.

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terns See LARIDAE.

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Tern

set of three; trio; triplet; a group of three stanzas in poetry, 1856.

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tern sea-bird of the genus Sterna. XVIII. of uncert. orig.

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