Common TernSterna hirundo

adult, breeding
Arthur Morris/VIREO
immature (1st winter)
Arthur Morris/VIREO
juvenile
Arthur Morris/VIREO
adult, nonbreeding
Arthur Morris/VIREO
adult, breeding
Johann Schumacher/VIREO

Description

One of four very similar terns on this continent. The species lives up to its name as a "common" tern mainly in the northeast; over much of the continent, it is outnumbered by the similar Forster's Tern. Also widespread in the Old World.

Habitat

Lakes, ocean, bays, beaches. Wide range of aquatic habitats in summer, both coastal and inland waters in low-lying, open country, where shallow waters for fishing are close to undisturbed flat islands or beaches for nesting. Winters mostly along coastlines in warm subtropical or tropical waters.

Feeding Diet

Mostly fish. Feeds on a wide variety of small fish, focussing on whatever types most easily available, sometimes concentrating on shrimp instead. Also eats other crustaceans, insects, marine worms, small squid, leeches, marine worms.

Feeding Behavior

Forages mostly by flying over water, hovering, and plunging to catch prey below surface. Sometimes dips down to take items from surface of water, or pursues flying insects in the air. Occasionally steals food from other terns.

Nesting

Usually first breeds at age 3-4 years. Nests in colonies, sometimes in isolated pairs. In aerial courtship, groups and pairs perform high flights. Male may fly over colony carrying fish; female follows. On ground, pair postures, bows, struts in circles; male presents fish to female. Nest site is on bare ground or surrounded by low vegetation; sometimes on floating mat of dead vegetation. Nest (built by both sexes) is shallow scrape in soil, usually lined with bits of plant material and debris. Eggs: 1-3. Variable, buff to pale blue or olive, marked with brown and black. Incubation is by both parents (female may do more), 21-25 days. Young: Leave nest after a few days but remain nearby, are fed by both parents. Age at first flight about 22-28 days; may remain with parents another 2 months or more. One brood per year, rarely two.

Eggs

1-3. Variable, buff to pale blue or olive, marked with brown and black. Incubation is by both parents (female may do more), 21-25 days. Young: Leave nest after a few days but remain nearby, are fed by both parents. Age at first flight about 22-28 days; may remain with parents another 2 months or more. One brood per year, rarely two.

Young

Leave nest after a few days but remain nearby, are fed by both parents. Age at first flight about 22-28 days; may remain with parents another 2 months or more. One brood per year, rarely two.

Conservation

Northeastern populations probably much lower than they were historically. Numbers reduced by plume hunters in late 1800s, increased again with protection early in 20th century, then declined again as populations of predatory large gulls increased in that area. Coastal Common Terns are more and more concentrated in a few well-protected colonies. Some inland populations are declining as well.

Range

After breeding, may move a short distance north before beginning southward migration. Almost none actually overwinters in North America, although fall migrants may linger to the beginning of January. Winter range is along tropical coasts as far south as Peru and Argentina. Stray Common Terns in Alaska are from a dark-billed race in eastern Asia.

Listen

keearr calls #1
churring calls at net
kip alarm calls
keearr calls #2

Similar Species

adult

White-winged Tern

This Eurasian species, rare in our area, is similar to Black Tern and usually associates with it. Most often seen with flocks of migrant Black Terns on the Atlantic Coast in late summer. It has also strayed from Asia to Alaska. There are a couple of instances of adults summering around marshes in the interior, and an adult once paired with a Black Tern in Quebec and nested there.

adult

Aleutian Tern

An uncommon bird, nesting around the Bering Sea and nearby waters, including much of the southern Alaskan coast and Aleutian Islands. May associate with Arctic Tern, but is far less numerous. Its habits have not been thoroughly studied. Its winter range was completely unknown until the late 1980s; now it is known that many Aleutian Terns spend the winter near the Equator in the western Pacific.

adult, breeding

Least Tern

Our smallest tern. Often seen flying low over the water, with quick deep wingbeats and shrill cries. Usually hovers before plunging into water for tiny prey; does more hovering than most terns. Populations are endangered in many areas because of human impacts on nesting areas, especially competition for use of beaches. However, Least Terns in some parts of the east are now nesting successfully on gravel roofs near the coast.

adult, breeding

Caspian Tern

The largest of the terns, larger than many gulls. Cosmopolitan, nesting on five continents. In North America, it is common along both coasts and locally inland, mainly around large bodies of water. Noted for its long adolescence, with the young dependent on their parents for many months; even in late winter, many an adult Caspian is trailed by a begging youngster from the previous nesting season.

adult, breeding

Roseate Tern

Widespread but very local on the coasts of six continents. In North America, only on Atlantic seaboard, mainly in northeast and Florida. More strictly coastal and oceanic than most similar terns. Has a very light and buoyant flight, with relatively fast and shallow wingbeats, and often gives a musical callnote in flight. Its numbers on this continent are in a long-term decline, probably owing to a combination of reasons, and it is now considered an endangered species.

adult, breeding

Forster's Tern

Several of the terns are very similar in appearance. Forster's Tern looks so much like a Common Tern that it was largely overlooked by Audubon and other pioneer birders. However, Forster's is more of a marsh bird at most seasons, especially in summer, when it often nests on top of muskrat houses. Unlike Common Tern, Forster's regularly winters along our southern coasts.

adult

Arctic Tern

Famous as a long-distance champion: some Arctic Terns may migrate farther than any other birds, going from the high Arctic to the Antarctic. Breeds on coasts and tundra from New England, Washington, and Britain north to the northernmost limits of land, and spends the rest of the year at sea. Its migrations take it to every ocean, and to the vicinity of every continent. In North America, seldom seen from land south of its breeding grounds.

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