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Platte River Status: A rare migrant and uncommon and local nesting species. Occurrence dates at the Mormon Island Crane Meadows, Hall County, extend from 11 May to 4 September. Tout (1947) recorded least tern as a regular nesting species along the Platte River in Lincoln County present 30 April to 21 September. On 16 June 1926, Tout described "a cloud of least terns (that) filled the air" along the South Platte River west of North Platte. Wycoff (1960) reported on 17 years observations at a nesting colony near Lexington, Dawson County; the species is no longer extant as a nesting bird there.

Breeding Range: Currently restricted to widely-distributed areas of the Platte River Valley, primarily in the Big Bend reach between Kearney and Grand Island. Historically, least tern was much more widespread, occurring regularly on the South Platte River west of North Platte (Tout 1947).

Breeding Population: Between 65-80 nesting pairs are estimated in the study area annually based on the maximum number of nests located. Faanes (1983b) found 17 nests in the Big Bend reach of the Platte River in 1979.

Habitat: Least tern nests on barren riverine islands. Faanes (1983b) described habitat characteristics at least tern nest sites along the Platte River. The amount of bare ground within 1 m. of the nest averaged 72%, and herbaceous vegetation made up 18%, indicating the strong preference of this species for nearly bare areas for nest placement. A shallow, constant, supply of water that serves as a source of fishes is an essential component of nesting habitat. In periods when suitable nest habitat is not available on the open river channel (during floods), least tern will nest on the sandy beach zone of sandpits immediately adjacent to the river. Existing data (NGPC 1986) suggest that sandpit sites are less desirable because of high nest predation rates, and excessive human disturbance. Colony size can range from a few to several hundred nesting pairs, and colonies can be subdivided (Massey 1974). Habitat loss can lead either to a decrease in colony size (Varza 1975) or site abandonment (Burger 1984). Erwin (1977) stated that because of shifting nest site locations, a larger amount of habitat than is being used at a particular time should be protected to accommodate future habitat needs.

Effect of Habitat Alteration: Least tern has been severely impacted by de-watering of the Platte River system and the subsequent encroachment of wooded vegetation within the river channel. Although this species can adapt to natural variability in river flows, recent human influences resulting in drastic changes in the flow regime have severely impacted the distribution and abundance of the bird along the Platte River and throughout the Great Plains. Wycoff (1960) chronicled movements of a Dawson County nesting colony as the birds attempted to adapt to increasing intensity of wooded vegetation encroachment. Eventually the colony became extinct. Vegetation encroachment on sandbar nesting habitat is a major cause of habitat loss (Ducey 1981). Human related disturbance through foot traffic, feral animals, and off-road vehicles has caused nest desertion in the study area (Faanes 1983b). Least tern can nest successfully near human activity if the nest itself is not disturbed (Craig 1971, Thompson 1982).

Nesting Data: Extreme egg dates at the Mormon Island Crane Meadows, Hall County extend from 21 May to 9 August. Recently fledged birds have been observed there between 24 July and 30 August. The ability of this species to nest over a 2-month period reflects the resiliency of least tern in adapting to the unpredictability of available nesting habitat. Tout (1947) reported active nesting attempts in Lincoln County between 19 May and 17 August. Benckeser (1948) found six least tern pairs and three nests on a sandbar in the South Platte River 3 km east of Brule, Keith County, on 10 July 1948.