Original description: Spizella taverneri Swarth and Brooks 1925
Taxonomic history in AOU/AOS Check-list
AOU 4 (1931): Timberline Sparrow, Spizella breweri taverneri
AOU 5 (1957): Brewer’s Sparrow, Spizella breweri taverneri
AOU 6 (1983): Brewer’s Sparrow, Spizella breweri
AOU 7 (1998): Brewer’s Sparrow, Spizella breweri [taverneri group]
Behavior: The Brewer Sparrow tends to be relatively confiding, both on the breeding grounds and, especially, in winter, when flocks often allow close approach before darting into vegetation. In contrast, the Timberline Sparrow in its nesting range is reported to be “extremely wary,” and to flush quickly when disturbed, often perching at the top of a bush or tree, nervously flicking its tail.
Timberline Sparrows feed singly, in pairs, in family groups, and in winter presumably in flocks, scratching on the ground beneath shrubs or in the open. Their flight is likely similar to that of the Brewer Sparrow: rapid, swooping but direct, usually landing on top of or just inside the foliage of small trees and bushes.
Voice: If visual identification is challenging, the vocal distinctions between singing male Brewer and Timberline Sparrows are somewhat more pronounced. Both have two song “types,” a short song comprising one to three different trills and a long song made up of five to ten different trills and syllables. The short song of the Timberline Sparrow appears to be relatively little known, but its long song differs from that of the Brewer in lacking that species’ distinctly buzzy tone thus making a “more musical and tinkling” impression. In Alaska, and probably throughout their range, Timberline Sparrow males frequently repeat segments within the long song; the only component of the Brewer Sparrow’s long song to be repeated is “a series of descending sweet notes” without counterpart in the songs of Timberline Sparrows.
The short song of the Timberline Sparrow probably also averages “less broadband and more musical,” but there may be overlap—and it is more difficult for the human observer to gain an accurate impression of a song of such brief duration.
Detailed description and measurements drawn from standard reference works
Adult: Tail feathers dusky brown. Upper tail coverts and rump plain brown, perhaps lightly tinged gray. Back and scapulars brown with light gray tinge; heavy blackish shaft streaks. Primaries and secondaries dark brown with narrow buffy grayish edges. Tertials dark brown with buffy grayish edges, broader on outer web. Greater and median coverts with dusky brown centers, broad buffy grayish edges and tips forming rather broad but low-contrast wing bars. Nape with variably broad clear gray collar, streaked sparsely to moderately black, heaviest at center.
Under tail coverts, vent, and belly dull grayish or whitish. Breast and flanks grayish with variable fine, sparse dusky streaking. Throat dull white, separated from dull whitish jaw stripe by narrow dark lateral throat stripe. Ear coverts brownish gray.
Crown brown, finely streaked dusky, the streaks often concentrated into dark lateral crown stripe. Usually a dull whitish or brownish median stripe with sparse dusky streaking. Brownish gray ear coverts divided from jaw stripe by narrow dusky, evenly narrow along its entire length. Dusky eye line, paler and narrower than lateral throat stripe, borders ear coverts above behind eye. Narrow white complete eye ring; may be barely broken by eye line at rear of eye. Fairly conspicuous pale brownish gray supercilium continues onto pale, unmarked lore.
Tarsus and toes pale brownish pink, averaging darker than in Brewer Sparrows. Narrow, short but slender bill brownish above, flesh-colored below, with black tip.
Length 137 mm (5.4 inches)
Wing 60-66 mm (2.4-2.6 inches)
Tail 57-68 mm (2.2-2.7 inches)
Mass 10-14 g