Brewer’s Sparrow

The Brewer’s Sparrow is the smallest sparrow. Its plumage is subtle and undistinguished. Two species are generally recognized, S. b. breweri and the ‘Timberline’ sparrow, S. b. taverneri. Each has different breeding ranges, which may overlap, and have subtle plumage differences. The breeding ranges are eastern Alaska, Yukon, central south BC, east to southeast Saskatchewan, south to New Mexico, Arizona and south central California. It is absent from the pacific coastal areas and winters in southwest US and northern Mexico.

Adult (spring/summer)
The head is very subtlety streaked. The supercilium is pale dull gray to dull whitish. The eye is dark with a white eye ring. Moustachial and malar stripes are thin and brown. The bill is small, conical, pale brown with dusky tip. Nape and mantle streaked. The rump is brown with dark brown streaks. Wings are brown with poorly defined wing bars. Tail is long, notched and brown. Underparts are pale and unstreaked, breast and flanks dingy gray, sometimes lightly streaked under the wings. The belly is dull white, legs and feet are pale pink or pale horn colour. Length: 12-13cm. Weight: 10.5g.

No distinguishing differences between male and female.

Juvenile: Similar to adults but less streaked above with breast and flanks narrowly streaked with black triangular markings.

General:

The smallest and slim sparrow.
Length: 12-13cm. Wing: 66.2-60.0. Weight: 10.5 grams.

Behaviour:

Quite inconspicuous on the breeding ground where most activities take place undercover of vegetation. Hops on the ground; occasionally runs. Hops or clambers about among twigs and branches within shrubs. Main foods taken are small insects, mainly gleaned from foliage and bark of shrubs or dwarf trees; also seeds usually taken from ground. Although its bill morphology is typical for a sparrow, much of this species’ diet consists of arthropods. As benefits an arid land species, its water economy is excellent and can exist for long periods without drinking.

Habitat:

Breeds in a variety of habitats, but in the southern parts of their range they prefer big sagebrush and silverberry in short grass. The northern population is found in subalpine fir and krummholz. Winters in loose flocks in arid brushy areas with patches of grass.

Information:

Shortly after arrival on the breeding grounds Brewer’s pairs build a small open-cup nest in sagebrush and lay 3 bluish-green marked with brown eggs.

Similar species:

Conservation Status:

Numbers have dropped by approximately 60% since 1961. The reasons for this are unclear but reflect habitat destruction.

Capture Rates

Brewer’s Sparrow breeds in the landscape of the intermountain west dominated by sagebrush. Therefore, it is a vagrant visitor to Colony Farms as is reflected by a single capture in June.

Molt Summary:

PF: HY partial (Jul-Oct), PB: AHY complete (Jul-Oct); PA limited – partial (Feb-May).
Preformative and prebasic molt commences on the breeding grounds with some HYs and occasional AHYs completing the molt on the winter grounds.
Preformative molt usually includes all med and gr covs, usually 1-3 terts, and occasionally 1-2 central rects.
Adult PB: a few flight feathers occasionally can be retained until the winter grounds, especially middle ss (among s3-s6).
1st PA: includes 0 – 5 inner gr covs, usually 1 – 3 terts, and occasionally s6, but usually no rects.
Adult PA: includes 0 – 4 inner gr covs and often 1 -3 terts, but usually no rects.

Has indistinct streaking on the breast and flanks and buff-tipped gr covs.

Juv M = F

1-3 terts usually replaced, contrasting with the older middle ss in Sep-Mar, or if all juvenal terts are replaced, these are relatively worn and edged buff; outer pp covs narrow , tapered, relatively abraded, and pale brown with indistinct, narrow , or no buff edging contrasting with the slightly fresher and darker-centered gr covs; central rects (r1) occasionally replaced and contrastingly fresh ; outer rects tapered and relatively abraded.

Terts and middle ss (s4-s6) uniformly adult and edged whitish; outer pp covs broad, truncate, relatively fresh, and dusky brown with relatively distinct ands broad, whitish edging, not contrasting markedly in colour or wear with the gr covs; rects uniformly adult, truncate, and relatively fresh.