Associated Species: Other species that may use habitat in a similar way and/or respond similarly to threats, management, and conservation activities include Snowy Plover, Piping Plover, Killdeer, American Avocet, Black-necked Stilt, and Spotted Sandpiper.

Distribution: Least Terns nest along the East, West, and Gulf coasts, and inland along the Missouri and Mississippi river drainages. In Physiographic Area 36 in Colorado, they nest only on reservoirs in the vicinity of the Arkansas River, between Las Animas and Lamar.

Habitat Requirements: Least Terns nest on sandbars, islands, beaches, and alkali flats with little or no vegetation, although they will tolerate more vegetation than the plover species. Vegetation provides thermal and hiding cover for chicks later in the season. Nests are often located within 20 m (65 ft) of water. Nesting success is higher on islands than on the mainland, probably due to restricted access by terrestrial predators.

Ecology: These semi-colonial terns place their nests from a few meters to hundreds of meters apart from one another. Adults arrive in Colorado in mid May and initiate nesting between late May and early July. Most young leave the nest by mid August, and most birds leave the state by mid September. Least Terns winter in Central and South America. They feed primarily on fish, but may also take terrestrial and aquatic invertebrates.

Management Issues and Conservation Recommendations: Disturbance or destruction by humans and domestic animals often leads to nest failure. Least Terns will accept artificial islands for nesting, but they will not use freshly made islands until the soils have settled and become stable. Management efforts, including alteration of water management schemes and habitat manipulation, should follow the guidelines of the federal and state recovery plans (Sidle and Harrison 1990, Slater 1994).

Status and Reasons for Concern: This species is listed as Endangered at the federal and state (Colorado) levels. Fewer than 50 pairs breed in Colorado. Due to its small numbers and limited range, this species is not monitored by the BBS. This species is monitored by CDOW and USFWS.

Biological Objective: Increase the species' distribution and abundance, based on results of CDOW censuses or other monitoring programs.

Selected References: Andrews and Righter 1992, Kingery 1998, Thompson et al. 1997.