Montana Field Guide

Slight sexual size dimorphism; sexes otherwise similar in appearance. Finely streaked brown crown; median crown-stripe frequently absent, but sometimes an indistinct one is present. Pale gray supercilia, unmarked lores, and bold, complete white eye-ring. Auricular brown, softly outlined with black and bordered below by grayish white submustachial stripe; black malar streak thin, often indistinct. Underparts dull white, with grayish flanks. Breast unstreaked in adult, although sometimes flanks are streaked. Back and rump brown, the latter streaked with black. (Rotenberry, J. T., M. A. Patten, and K. L. Preston. 1999. Brewer’s Sparrow (Spizella breweri). In The Birds of North America, No. 390 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.)

In the Bozeman area, normal migration periods are from May 15 to 25 and in mid-August (Skaar 1969).

In sagebrush areas in central Montana, Brewer's Sparrows nested in sagebrush averaging 16-inches high. The cover (concealment) for the nest provided by sagebrush is very important (Best 1970).

In central Montana, food volume was 71-81% animal (Coeopterans and Hemipterans) and 8-17% plant (grass seeds). Chemical spraying led to a greater dependence on plants (Best 1970). 59-69% of the food was grasshoppers, leaf (Chrysomelidae) and snout (Curculionidae) beetles.

In central Montana, an average of 37 breeding pairs were found per 100 acres.

In central Montana, 74% of nests were found between 6 to 8 inches above the ground in big sagebrush plants. The average clutch size was 3.26. Statewide, the species nests from mid-June to mid-July (Davis 1961).