E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Spizella breweri Cassin, 1856
Brewer`s Sparrow
Family: Passerellidae

Species account author: Jamie Fenneman

Photo of species

© Tim Zurowski  Email the photographer   (Photo ID #8152)


Distribution of Spizella breweri in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Adult
The upperparts (back, scapulars, rump) are buffy-brown to greyish-brown, with narrow blackish streaks on the back and scapulars. The wings (uppering coverts, flight feathers) are dark brown with extensive pale buffy-brown feather edges, sometimes forming two indistinct buffy-brown to buffy-white wing bars. The relatively long, slender, shallowly notched tail is dark brown with paler buffy-brown feather edges. The underparts are whitish or greyish-white to pale buffy-white, with a grey wash on the sides and flanks. The crown and forehead are buffy-brown with fine, narrow, black streaks. The nape and hindneck are pale buffy-grey with fine, relatively indistinct darker streaks. The broad supercilium is pale greyish-white and the ear coverts are pale brown with a narrow darker brown post-ocular stripe along their upper margin as well as a thin darker brown stripe along their lower margin. The throat is whitish to greyish-white and is separated from the buffy-white to greyish-white moustachial area by a thin, blackish or dark brown malar stripe. There is a narrow, but conspicuous, complete whitish eye-ring. The iris is dark, the short, conical bill is dull pinkish with dark brown along the culmen and at the tip, and the legs and feet are pinkish. Birds in fresh non-breeding plumage (mid-summer to fall) are less boldly marked than birds on the breeding grounds, and appear overall more drab and buffy.

Juvenile
This plumage is held until late summer (August) of the first year. It is overall similar to the plumage of the adult, but is buffier, with a less distinct head pattern, more prominent buffy wing bars, and extensive dark brown streaking on the breast, sides, and flanks. See ‘Taxonomy’ for differences in juvenal plumage between the subspecies.

Measurements
Total Length: 13-14 cm
Mass: 9-14 g

Source: Rotenberry et al. (1999); Sibley (2000)

Biology

Identification

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.
Vocalizations

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)

Breeding Ecology

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.
Foraging Ecology

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)

Habitat


The habitat preferences of the two subspecies of Brewer’s Sparrow differ dramatically. Birds breeding in the south-central interior (S.b.breweri) are essentially confined to arid shrub-steppe where they breed colonially in stands of mature Big Sagebrush in dry grasslands. Some populations of S.b.breweri occur at middle to high elevations (such as at Mt. Kobau near Osoyoos), but are still confined to isolated pockets of the montane subspecies (vaseyana) of Big Sagebrush. In contrast, birds breeding in eastern and northern B.C. (S.b.taverneri) occur primarily in high elevation brush, particularly where extensive stands of willow, alder, or birch occur among stunted fir and spruce trees in subalpine parkland, on avalanche slopes, or in alpine basins. This subspecies is found only at elevations between 850 and 2,040 m, with birds occurring at lower elevations in northern B.C. or locally in southeastern B.C. where suitable brushy habitat extends into otherwise uninhabitable montane coniferous forests. Some colonies at low elevations in eastern B.C. (in the southern Rocky Mountain Trench) are found in dry Antelopebrush scrub in open Ponderosa Pine forests. Although this habitat is very different from that which is normally occupied by the subspecies, historical accounts and collected specimens have shown that these birds are indeed S.b.taverneri.

Source: Rotenberry et al. (1999); Campbell et al. (2001)

Distribution

Global Range

S.b.breweri breeds from south-central British Columbia, southern Alberta, and southern Saskatchewan south through the western United States to southern California, northern Arizona, and northern New Mexico, ranging east as far as the western Great Plains. S.b.taverneri breeds in eastern Alaska, southwestern Yukon, and northwestern British Columbia, as well as along the Rocky Mountains in eastern B.C., western Alberta, and extreme northwestern Montana. The species (both subspecies) winter in the southwestern United States from southern California east to western Texas, and south through northern and central Mexico.
BC Distribution

Breeding
Uncommon and highly local in the southern Okanagan Valley and lower Similkameen Valley of the south-central interior. It is very rare during the breeding season in the the Thompson Basin (Kamloops, Cache Creek, etc.) and may breed sporadically in this area as well. It is also uncommon and local at high elevations along the Rocky Mountains in eastern B.C. (north at least as far as Mount Robson), as well as in the extreme northwestern portion of the province (Haines Triangle, Atlin area). Observations of singing, territorial males in the northern Rocky Mountains (Stone Mountain, etc.) and along the eastern slopes of the Coast Mountains south to the Chilko Lake area suggest a more widespread breeding range in the province. This species may prove to be a rare to uncommon breeder throughout much of the northern one-third of the province east to the Rocky Mountains, as well as south along the Coast Mountains, but much of this area is largely inaccessible and it has not yet been documented from vast portions of this region.

Migration and Vagrancy
The Brewer’s Sparrow (S.b.breweri) is an uncommon spring and fall migrant in the southern Okanagan Valley away from known breeding colonies; most individuals appear on and depart from the breeding colonies directly and are not seen during migration. The subspecies S.b.taverneri has been documented during spring migration from the Okanagan Valley of the south-central interior, suggesting that it may move through this area of the province along with the larger numbers of S.b.breweri. It is casual to very rare farther north in the southern interior as far as the Williams Lake area, with individuals representing both S.b.breweri and S.b.taverneri. It is also casual to very rare at low elevations during spring and fall migration throughout the eastern and central portions of the province, with most or all of these birds attributable to the subspecies S.b.taverneri. It is casual to very rare during spring and fall migration on the south coast (Lower Mainland, southern Vancouver Island); most vagrants on the south coast are attributable to S.b.breweri, although there is at least one spring record of S.b.taverneri from the Lower Mainland.

Spring migrants (S.b.breweri) begin to appear on the breeding grounds in the southern interior during late April or early May (exceptionally in early April), although most individuals do not appear until mid-May; the peak spring migration in the south-central interior is during late May. In eastern B.C., S.b.taverneri does not appear on the breeding grounds until late May, with most arriving between late May and mid-June. In the northwestern parts of the province, S.b.taverneri arrives on its breeding grounds very late, with the earliest arrivals not occurring until mid-June (peaking in late June and early July). Spring vagrants along the coast occur between mid-April and mid-June, with most occurring in May.

Fall migrants (S.b.breweri) depart the breeding grounds in the south-central interior during the first half of August, with occasional individuals lingering as late as early September (exceptionally into late September). Similarly, populations of S.b.taverneri in the northwestern and eastern areas of the province depart the breeding grounds between late July (in northern areas) and late August, with occasional individuals lingering in southeastern B.C. as late as late September. Most individuals of S.b.taverneri appear to depart directly from the breeding grounds and are not observed during migration. Fall vagrants along the south coast have been observed in late August and early September.

Source: Campbell et al. (2001)

Conservation

Population and Conservation Status

This species has undergone significant declines over much of its breeding range during the past 40-50 years, particularly during the past 20 years, with declines approaching 60% for some regions. Curiously, however, the number of individuals detected on the wintering grounds has remained stable or even increased slightly (although not significantly). These declines are generally attributed to the destruction and degradation (through overgrazing, clearing, invasion of exotic plants, etc.) of mature sage habitat throughout the Great Basin and western Great Plains. An estimated 800-1,000 Brewer’s Sparrows of the nominate (breweri) subspecies breed in the southern Okanagan Valley of B.C., although it is unclear whether this population has been declining at the same rate as the population as a whole. However, because of its tiny range in the province and close association with a highly endangered ecosystem (arid sagebrush steppe), the breweri subspecies is currently classified as red-listed (endangered) by the British Columbia Conservation Data Centre (BC CDC). The abundance and distribution of the ‘Timberline Sparrow’ (S.b.taverneri) is very poorly known throughout the province but is likely stable, although it may be susceptible to the effects of global warming which could reduce or eliminate some areas of suitable breeding habitat.

Source: Rotenberry et al. (1999); Campbell et al. (2001); Beadle and Rising (2002)

Taxonomy


This species is closely related to both Chipping Sparrow and Clay-colored Sparrow, and has hybridized with both species in areas where their ranges overlap. Two subspecies of Brewer’s Sparrow are currently recognized, both of which are found in British Columbia. These two subspecies differ subtly but consistently in plumage and song, but differ significantly in habitat and range. The two subspecies were initially described as separate species, and many current authors continue to recognize this treatment. Recent studies of the genetics and ecology of these two forms have supported their recognition as separate, though recently divergent, species, and it is reasonably likely that the two forms will be re-split in the future.

The subspecies in B.C. are as follows:

Spizella breweri breweri
This subspecies breeds in arid sagebrush scrub in the south-central interior, as well as in similar habitats throughout the western United States and prairie provinces of Canada. It is slightly smaller than S.b.taverneri, but has a slightly larger and more extensively pinkish bill. It is overall paler and browner than S.b.taverneri, with finer dark streaking on the upperparts and a less boldly contrasting head pattern.

Spizella breweri taverneri Swarth & Brooks
This subspecies is widely known as the ‘Timberline Sparrow’. It breeds in open, brushy willow-birch-alder scrub at subalpine and alpine elevations in the mountains of eastern B.C. (south into northwest Montana and east into western Alberta) as well as in the far northwestern areas of the province (ranging north into the Yukon and Alaska). Individuals observed in subalpine habitats along the eastern slopes of the Coast Mountains are also likely of this subspecies. It is slightly larger than S.b.breweri, but has a slightly smaller, darker, and more slender bill. Its plumage is slightly darker and greyer than S.b.breweri, with heavier black streaking on the upperparts and a bolder and more contrasting head pattern. The breast is slightly darker and greyer, contrasting more noticeably with the paler belly, and it sometimes shows some fine dark streaking on the breast and flanks when in fresh plumage. Birds in juvenal plumage are darker and more heavily streaked overall than juvenile S.b.breweri. In many respects, this subspecies is intermediate in plumage between nominate S.b.breweri and Clay-colored Sparrow. The song of S.b.taverneri also differs slightly from that of the nominate subspecies (see ‘Vocalizations’).

Source: Rotenberry et al. (1999); Campbell et al. (2001); Beadle and Rising (2002)

Status Information

Scientific NameOrigin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
Spizella breweriNativeS4?BYellowNot Listed
Spizella breweri breweriNativeS2S3BBlueNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-07-15 4:00:27 AM]
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