New York Status: Threatened
Federal Status: Endangered (interior U.S. only, not on coast)
The least tern is the smallest American tern, weighing about 1 ounce and measuring about 9 inches in length. It is identified in spring and summer by a white forehead contrasting with a black crown and nape. Its body is slate grey above and white below, with the pointed wings and forked tail characteristic of most terns. The bill and feet are yellow. Wingbeats are uniquely rapid and the black leading edge of the outer wing is conspicuous in flight. Immature least terns have upper parts which are mottled white and dark brown. The call is either a sharp, penetrating "kip-kip-kip" or a shrill "zreep."
By late April to mid-May, the least tern is on its northernmost breeding grounds, usually arriving before common terns and black skimmers. The least tern breeds in colonies of up to 200 birds. Nests are scraped in sand or gravel, and may be lined sparingly with small shells or other debris. Eggs are commonly laid in clutches of 2 from late May through June, and are incubated by both sexes for 21 days. The young fledge in 19-20 days. The least tern is very defensive in the colony, and adults scream and dive at intruders. Piping plovers, another endangered beach-nesting bird, are commonly found nesting in association with least terns. By late August and early September, least terns leave their northern breeding grounds to head for wintering areas.
Least terns feed mostly on small fish caught by skimming the surface of the water or by making dives from the air. Banding studies have shown individuals living up to 21 years.
Distribution and Habitat
The least tern has a nearly worldwide distribution. In the Western Hemisphere it breeds on the Pacific Coast from Central California to Peru; inland along the Colorado, Red, Rio Grande, Missouri, and Mississippi river systems; on the Atlantic Coast from Maine to Argentina; and along the Great Lakes in Michigan, Minnesota, Wisconsin, and Ohio. Migrants mainly occur on Long Island's outer coast and rarely on the lower Hudson River. This species winters from the Gulf Coast and Central America south to Peru and Brazil.
The least tern breeds on broad, level expanses of open sandy or gravelly beach, dredge spoil and other open shoreline areas, and more rarely, inland on broad river valley sandbars. In an unusual case, 20 pairs nested on the roof of a city auditorium in Pensacola, Florida in 1957, and have continued to do so annually.
The U. S. Fish and Wildlife Service lists the least tern population found in the interior U. S. as endangered. Around the turn of the century, the least tern was in danger of extirpation in the northeastern U. S. because of hunting for the millinery trade. Protective legislation in 1918 allowed the species to recover in the 1920s and 1930s. In recent years, however, human pressures have been causing a decline in populations of this species. Surveys from 1985-1995 found an average of approximately 3,000 breeding pairs at between 50 and 66 colonies along New York's Long Island coast.
Development of coastal areas destroys breeding habitat and recreational activities can disrupt reproduction. Increases in populations of more aggressive gulls has led to competition for nesting sites. Some colonies are severely limited by predation from rats, great horned owls, black-crowned night herons, dogs, and cats.
Management and Research Needs
Researchers from private and public conservation organizations and concerned volunteers annually census breeding colonies on Long Island. With the cooperation of landowners, nesting areas are fenced off and signs are posted in an attempt to protect colonies from disturbance. Tern stewards monitor colonies and provide information to the public about this and other beach-nesting species. Extermination of rats has been undertaken in several areas.