Brewer’s Sparrow is a very drab sparrow and is easily confused with the two other members of the genus Spizella with which it often occurs, especially in juvenal plumage. Adult Brewer’s Sparrow is most likely to be confused with adult Clay-colored Sparrow, particularly during fall migration when Clay-colored Sparrows are in non-breeding plumage. Brewer’s Sparrow is an overall drabber species with a much less strongly contrasting head pattern than Clay-colored Sparrow. Even in non-breeding plumage, Clay-colored Sparrow shows a very bold head pattern with a whiter and more sharply contrasting supercilium, darker and browner ear coverts, and a bold grey patch across the nape and sides of the neck. Brewer’s Sparrow can also reliably be told from Clay-colored Sparrow by its narrow, nut nonetheless distinctive, complete whitish eye-ring that is obvious on the overall subdued face pattern. The pale eye-ring of Clay-colored Sparrow is less distinctive and does not stand out as much on the more strongly patterned face. Juvenile Clay-colored and Brewer’s Sparrows are very similar, but still show the differences in facial pattern that are present in adults (e.g., duller and less contrasting head pattern in juvenile Brewer’s Sparrow). Both species molt out of juvenal plumage prior to fall migration, so this plumage should present an identification concern only for a brief period on the breeding grounds.
Chipping Sparrow overlaps in range with Brewer’s Sparrow throughout its range, but fortunately breeding-plumaged adults are brightly marked and are extremely unlikely to be confused with adult Brewer’s Sparrows. Even non-breeding adult Chipping Sparrows, which are infrequently observed in B.C., can be distinguished by their face pattern (dark eyeline, black-streaked rusty-tinged crown, lack of whitish eye-ring) and should be easily distinguishable from adult Brewer’s Sparrow. Juvenile Chipping Sparrow, however, is similar to juvenile Brewer’s Sparrow and should be identified with caution. There is a suggestion of the diagnostic face pattern as is found in the non-breeding adult, however, which can be an aid in separating the two species. In addition, juvenile Chipping Sparrow has a greyer rump than juvenal Brewer’s Sparrow. Chipping Sparrows retain juvenal plumage throughout fall migration, unlike Clay-colored or Brewer’s Sparrows, so any juvenile Spizella observed during migration in B.C. has a high likelihood of being a Chipping Sparrow.
| The primary song (‘Long Song’) is a long, varied series of trills and buzzes with an overall descending pattern: zerr-zerr-zerr, tir-tir-tir-tir, cheeeeeeee, dee-dee-dee, zrrrr-zrrrr-zrrrr, zreeeeee…… A secondary song, known as the ‘Short Song’, is composed of a higher-pitched, faster trill followed by a (usually) lower-pitched, slower trill: bzzzzzzzz, chip-chip-chip-chip-chip. The songs of the two subspecies are similar, but those of S.b.taverneri are slightly lower-pitched, clearer, and less buzzy than those of S.b.breweri, with slower and more musical trills. Call notes (similar in both subspecies) include a high, sharp tsip and a short, weak, rising swit. Source: Rotenberry et al. (1999); Sibley (2000) |
Courtship
Other than occasional courtship feeding during early stages are pair formation, the primary means of courtship display appears to be the male’s song. The male begins singing shortly after arriving on the breeding grounds, usually perching on an exposed branch at the top of a large sagebrush shrub and singing for prolonged periods. Once the pair has been established, the male closely follows the female until she solicits copulation. This species appears to be loosely colonial, with breeding pairs congregating in relatively discrete patches of suitable habitat.
Nest
Nest building occurs shortly after the establishment of pair bonds, with most nests constructed during mid- to late May in B.C. The nest is constructed over 4-5 days with most construction being done by the female (although the male will contribute some material). It is usually situated low in a large, dense shrub that is generally larger and denser than the surrounding shrubs; the nest is rarely placed on the ground amongst dense grasses and forbs. Most nests of S.b.breweri are placed in sagebrush shrubs, although occasional nests have been found in other species such as snowberry, rabbit-brush, antelopebrush, and snowbrush; nests of S.b.taverneri have been found in juniper and birch shrubs. Nest heights range from 0-1.8 m, although most are placed 20-50 cm from the ground. The nest is a small cup (7-15 cm across, 3-5.5 cm deep) composed of small twigs, dry grasses, weed stems, and rootlets and is lined with fine grasses, small strips of bark, rootlets, and hair.
Eggs
A clutch of (2) 3-4 (5) eggs is laid between mid-May and mid-June in S.b.breweri and in mid- to late June in S.b.taverneri. The nominate subspecies is often double-brooded, and second clutches are laid in early to mid-July; S.b.taverneri does not appear to be double-brooded. The eggs are incubated by both sexes (primarily by the female) for 10-13 days. The smooth, slightly glossy eggs are blue-green and marked with reddish-brown blotches, speckles, and spots (usually concentrated around the larger end of the egg). Eggs have been documented in B.C. between mid-May and late July. The nominate subspecies is a regular host for Brown-headed Cowbird nest parasitism, and this has been documented on a number of occasions in southern B.C.
Young
The young are fully altricial upon hatching, with dark grey skin and patches of grey down; the bill is bright yellow and the gape is red. The nestlings are tended by both parents and remain in the nest for 6-9 days before fledging. Both parents continue to feed and tend to the young in the vicinity of the nest for several days following fledging, after which time they disperse and become independent. Nestlings and dependent fledglings have been observed in B.C. between late May and late August. The latest recorded fledglings (mid- to late August) have been associated with second broods of S.b.breweri, and most young S.b.taverneri disperse and become independent by late July or early August.
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Small insects and seeds comprise virtually the entire diet of this species throughout the year, with insects being overwhelming favoured during the breeding season and seeds forming the bulk of the diet during the winter. This is a relatively secretive species when foraging, with most of its food collected from within dense brush (it forages only infrequently in open areas, such as grassy areas or meadows). When disturbed, foraging individuals typically retreat quickly into dense cover and can be difficult to observe or dislodge from within. Insects are generally gleaned from the leaves, twigs, and branches of shrubs, while seeds are usually collected from the ground (rarely plucked directly from the vegetation). It occasionally flies 1-3 m into the air to catch insects in flight, especially during the late afternoon. During the breeding season, the male often intersperses bouts of singing with foraging activities. Foraging birds occur singly or in pairs during the breeding season, but congregate into loose (and often fairly large) flocks during migration.
Source: Rotenberry et al. (1999)
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