Least Tern
Least Terns are less reliant on islands for nesting than are most other terns. Inland populations of Least Terns nest in colonies on sandbars in rivers and coastal populations nest on beaches. Least Terns have even been known to nest on flat pebble-covered rooftops.

Abundant prior to the late 1800s, Least Terns were nearly annihilated along the Atlantic Coast by hunters seeking their plumes and skins. By the turn of the century, about 100,000 Least Terns were killed annually for the millinery trade. By the 1920s, the species had recovered strongly, thanks to federal and state legislation, including the landmark Migratory Bird Treaty of 1918. Today, however, the Least Tern is again in trouble. The interior populations are endangered and the coastal populations are threatened. Declines have been attributed to the loss of sandbar nesting habitat through the channelization and damming of rivers, and changes in river flow because of reservoir operations and barge traffic. At coastal nesting sites, increased use of recreational beaches has been a major cause of decline.

Least Terns nest in colonies on broad flat sandy beaches with little vegetation. Eggs and chicks are hard to see because of their cryptic coloration. Nests are shallow scrapes in the sand, occasionally lined sparingly with plant or shell fragments. Sometimes nests are only a few feet apart. The female lays two to three eggs that hatch after 19 to 22 days of incubation by both parents. During very hot weather, parents may soak their belly feathers in water and return to the nest to drip water on overheated eggs or chicks. Hatchlings are capable of leaving the nest when one day old, but they remain nearby. They can fly when they are 20 days old.

Least Terns feed on small fish ranging from 1 inch to 3 1/2 inches in length. They capture fish by hovering at heights of up to about 30 feet over shallow water, then plunge-diving to depths of 30 inches or less. They catch most prey just below the surface. They may eat prey while flying or carry their catch to the nest to feed to the hatchlings. Fledglings stay with the parents in small groups through the late summer.

The range of Least Terns extends along the Atlantic Coast from Maine to Florida and on the Pacific Coast from central California to southern Baja California. Historically, Least Terns were found along the Mississippi-Missouri River system and its tributaries, the Red River, the Ohio River and the rivers of central Texas. Least Terns still exist along these rivers today, but they are restricted wildlife refuges, reservoirs, and other areas with the least human disturbance. Most interior Least Terns are found along the lower Mississippi River. In early fall they migrate to their wintering grounds from the Gulf Coast and Central America, south to Peru and Brazil.
Least Tern Range Map

Description: The Least Tern is the smallest North American tern, approximately the size of a robin. Least Terns are buoyant and graceful flyers with more rapid wingbeats than larger terns. In flight the wings show a dark wedge on the outer primaries. Least Terns have pale gray upperparts, white underparts, and a short forked tail. The forehead is white, extending over the eye and forming a shallow V. The crown and nape are black. The black continues as an eyestripe to the base of the bill. The bill is yellow with a black tip, fading to gray, blackish or dull orange after the breeding season. The short legs are yellow, and the feet are webbed. Sexes are similar. Immature birds have darker plumage and bill than adults.


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