The least tern is the smallest of the North American terns. With a length of approximately nine inches, a wingspan of about 20 inches and light, buoyant flight, it gives the appearance of being very delicate on the wing. During the breeding season the adults are light gray on the upper parts, white underneath, with a black crown above the eyes and a white mark on the forehead. The legs and bill are yellow with the bill noticeably black at the tip. Unlike most other terns, the forked tail is relatively short.
Range: This bird breeds along the California coast, along rivers in the Mississippi Valley, and coastally from Maine south to Florida. It winters from Baja California south to southern Mexico and also along the coast of South America. In Colorado, the least tern has bred in the southeastern portion of the state, generally in the La Junta-Lamar area.
Habitat: The preferred nesting habitat is on sandy or pebbly beaches, well above the water line, around lakes and reservoirs or on sandy soil sandbars in river channels.
Diet: Least terns feed exclusively on small fish. When hunting, the least tern dives from as high as 20 feet into the water to capture their prey.
Reproduction: Least terns arrive to breeding grounds starting in mid-May. Females typically lay two to three eggs, deposited in a shallow "scrape". Both sexes share incubation, which takes about 19 to 25 days.
Endangered status: The least tern is listed as endangered in Colorado and federally. During the 1800s, the eastern coastal population of least terns was dramatically reduced as this bird was killed for its wings and feathers for the millinery trade. The population rebounded after receiving protection. Now, the population is declining again because of disturbance during the nesting season. Human recreational activity along beaches will cause these birds to abandon nesting activities, even after eggs have been laid. Another cause of nesting disruption is extreme water fluctuations during the nesting season in manmade lakes.
For more information, see the Natural Diversity Information Source species profile.