BREWER'S SPARROW - subspecies breweri (Spizella breweri breweri)
Two taxonomically distinct subspecies of the Brewer's sparrow occur in B.C. Spizella breweri breweri and S. b. taverneri. S. b. breweri is RED-listed because of its small population size
(800-1000 in B.C.) and restricted known breeding range. Unless otherwise noted, the remainder of this account refers to this subspecies.
The Brewer's sparrow breeds in sagebrush steppe in south-central B.C. Nests are almost invariably built in sagebrush plants, one sample (n=25) ranged in height from 64 to 170 cm (mean=110 cm). Nests are usually built near the ground, at an average height of 49 cm in one study and 30 cm in another. Typically 3-4 eggs are laid from mid-May to mid-June, and most broods have fledged by mid-July. The Brewer's sparrow is an opportunistic ground forager that feeds on seeds and insects, primarily on the open ground between and beneath the sagebrush plants. Wetlands and mesic ravines may be important insect foraging areas during the nesting season. Brewer's sparrows maintain small territories (approximately 2 pairs/ha) within semi-colonial aggregations.
CEI: (FRB - possible)
SOI: SOB, OKR, NOB, (THB - suspected)
BG: BGxh1 (BGxh2 - suspected, BGxh3 - possible)
ESSF: ESSFxc
IDF: IDFxh1, IDFdk1
MS: MSxk
PP: PPxh1, PPxh1a
Brewer's sparrows breed regularly south of Penticton to the U.S. border on the west side of the Okanagan valley, and in the Similkameen valley south of Keremeos. Ten major sites are currently on file with the CDC, which range from 350 m (east of Osoyoos) to 1800 m (Mt. Kobau). Breeding is strongly suspected in the Thompson Basin (Lac du Bois, Black Canyon, West Kamloops Lake and Perry Ranch) but this has yet to be confirmed. Singing males have also been observed near the confluence of the Fraser and Chilcotin Rivers, but it is unknown whether these represent breeding birds or unsuccessful outliers.
Wintering and migration
Brewer's sparrows arrive in B.C. from late April to early May, and depart from late August to early September to wintering areas in the southwestern U.S. and Mexico.
SS
2: herb
3a: low shrub
Brewer's sparrows are closely associated with extensive tracts of big sagebrush (Artemesia tridentata). Most breeding territories in the South Okanagan occur in fair and good range condition, but it is unclear if this represents selection of mid-successional plant communties or is a reflection of available habitat. Warm aspects (southeast to west) are primarily used for nesting, but this may simply reflect the distribution of sagebrush.
In Missouri, highest densities of S. breweri have been reported where silver sagebrush (A. cana) canopy coverage was approximately 50%, although some nesting occurred in areas of sparse (24%) and dense (81%) cover as well. In the Kobau/Kilpoola/Chopaka area of B.C., most Brewer's sparrows nest in big sagebrush with densities of 10-30% foliar cover. Grasslands with sparse sagebrush offer few sites for the construction of secure nests.
Dobler, F.C. 1990. Shrub steppe ecosystem studies. Phase one: Completion report for
1988-1990. Wash. Dep. Wildl. 13pp.
Harvey, D.H. 1992. The distribution, density and habitat of brewer's sparrows (Spizella
breweri) in the South Okanagan valley of British Columbia. B.C. Min. Environ.,
Penticton, B.C. Unpubl. Rep.
Resource Inventory Committee. [In prep]. Standardized inventory methodologies for
components of biodiversity in British Columbia: Forest and grassland songbirds. B.C. Min. Environ., Lands and Parks, Wildl. Br., Victoria, B.C.
Sarell, M.J. and K.P. McGuinness. 1996. Status of the Brewer's sparrow in British
Columbia. B.C. Min. Environ., Lands and Parks, Victoria, B.C. WR-77.
Walcheck, K.C. 1970. Nesting bird ecology of four plant communities in the Missouri
River Breaks, Montana. Wilson Bull. 82:370-382.
