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Platte River Status: A locally common summer resident at the extreme western edge of the study area. Tout (1947) considered Brewer's sparrow a rare and irregular migrant in Lincoln County. Rosche (1979) reported Brewer's sparrow at Cedar Point, Keith County during 18 July to 19 August 1977.

Breeding Range: Apparently restricted within our area to the dwarf sage region of the Western Plain physiographic region.

Breeding Population: The breeding population was estimated at 250 pairs during 1979-1980.

Habitat: We found the highest mean nesting densities (0.4 pairs/km²) in greasewood-dominated upland prairie. Kantrud and Kologiski (1982) characterized Brewer's sparrow nesting habitat in the northern Great Plains as lightly grazed black sage prairie where moundscale, greasewood, and dwarf sage were co-dominants. We found Brewer's sparrow in Deuel County in native grassland dominated by black sage, greasewood, blue grama, green needlegrass and eastern pricklypear.

Effect of Habitat Alteration: The reliance of Brewer's sparrow on lightly grazed native grasslands suggests that overgrazing of grassland habitat produces a negative impact on the species. Removal of shrubby vegetation from Brewer's sparrow habitat reduces the use of that habitat (Best 1972). Brewer's sparrow abundance did not change where up to 50% of the sagebrush in the area was removed, but total removal of sagebrush by herbicides caused a significant decrease in Brewer's sparrow abundance. Species use of a sagebrush area was reduced 99% within two years after herbicide spraying on a Wyoming study area (Schroeder and Sturges 1975). Given the small population size and specialized habitat requirements of this sparrow in the Platte River study area, conversion of suitable grassland habitat to agricultural production will contribute to a reduction in the nesting population.

Nesting Data: We have no confirmed records of nests or young from the study area. Colorado egg dates range from 28 May to 21 July.