Original description: Fringilla arborea Wilson 1810
Taxonomic history in AOU/AOS Check-list
AOU 1 (1886):Tree Sparrow, Spizella monticola; Western Tree Sparrow, Spizella monticola ochracea
AOU 2 (1895):Tree Sparrow, Spizella monticola; Western Tree Sparrow, Spizella monticola ochracea
AOU 3 (1910): Tree Sparrow, Spizella monticola monticola; Western Tree Sparrow, Spizella monticola ochracea
AOU 4 (1931): Eastern Tree Sparrow, Spizella arborea arborea; Western Tree Sparrow, Spizella arborea ochracea
AOU 5 (1957): Tree Sparrow, Spizella arborea arborea, Spizella arborea ochracea
AOU 6 (1983): American Tree Sparrow, Spizella arborea
AOU 7 (1998): American Tree Sparrow, Spizella arborea
IUCN Conservation Status: Of least concern
A truly abundant bird, the American Tree Sparrow has benefited from the historical remoteness of its breeding grounds and the ubiquity of its preferred brushy, weedy wintering habitat. Both of those circumstances are liable to change, as human disturbance increases at high latitudes and agricultural practices shift across the United States and Canada.
Global warming has shrunk this species’ winter distribution at its southern limits, but temperature change may, at least in the short term, also result in an expansion of its breeding range as warming trends allow the short woody vegetation American Tree Sparrows use as nest sites to spread farther north.
Behavior: The American Tree Sparrow is a bold, even curious bird in the winter, small flocks confidently feeding on the ground beneath bird feeders and on busy roadsides. Disturbed, they fly into bushes or low trees, neatly spacing themselves and staring back at the intruder. If the observer takes a step or two back, the birds often settle back to the ground and resume feeding, kicking and scratching on long, sturdy black legs and toes.
The Tree Sparrow’s powerfully swooping flight on relatively long, pointed wings and with little tail movement recalls that of a miniature Horned Lark. Longer flights usually end with the bird swooping upward to land on an exposed perch on a fence, bush, or telephone wire.
On migration and on the breeding grounds, males sing from similar low perches; countersinging, in which territorial males “answer” each other’s songs, is common.
Voice: American Tree Sparrows are quite vocal, even in winter, when the members of a flock often join in a rollicking chant of two- or three-syllable phrases tlee-dee, tleedle-dee. The alarm call, given by birds perched or in flight, is short and harsh, with an emphatic attack and very fast decay; it resembles the short flight calls of the Chipping Sparrow, but is briefer, with a more emphatic beginning and less prolonged ending.
Male American Tree Sparrows regularly sing on warm, calm days in late winter, and April migrants may sing persistently. Though the song is variable, individual males sing only a single type. All song types include a slow introductory series of sweet, clear notes, lower-pitched but otherwise reminiscent of a Brown Creeper’s song; most songs also have a fuller-voiced, accelerating second phrase, the final note often the highest-pitched of the song. In some birds, that second phrase ends with a sweet, slow tremolo followed by a high note. The clear, measured introduction is nearly distinctive, but can be confused with the imperfectly heard song of a distant fox sparrow.
Detailed description and measurements drawn from standard reference works
Adult Spizelloides arborea arborea: Tail feathers dark blackish gray with paler buffy to white edges. Rump and upper tail coverts dull light brownish tan, usually unmarked but sometimes with faint dark shaft streaks. Ground color of back grayish buff; back feathers conspicuously streaked black and rust. Scapulars grayish buff on inner webs, rust on outer webs. Primaries and secondaries dull blackish gray. Primaries with narrow white streak along shaft, secondaries with narrow dull rusty edge and dull buffy tips. Tertials with black centers and broad whitish tips; outer web of innermost tertial almost entirely white, of outer two tertials mostly bright rust. Greater coverts with blackish centers, rusty edges, and large white tips, forming conspicuous lower wing bar. Median coverts blackish with broad white tips, forming conspicuous upper wing bar. Nape light smoky gray.
Under tail coverts, vent, belly, and breast dull gray-tinged white. Flanks and sides of breast pale brown-buff, the color most extensive and darkest on the breast sides, where it bulges towards the center. Dusky spot on center of lower breast. Throat and jaw stripe light gray, slightly paler than breast; jaw stripe sometimes faintly bordered rusty above. Crown chestnut reddish; duller in winter, many feathers tipped dull buff and a central crown stripe often largely grayish. Ear coverts soft smoky gray, separate from broad gray supercilium by chestnut reddish eye line reaching from back of eye to side of nape. Supercilium palest above lore; lore gray with variable dusky or dull reddish spotting. Very narrow whitish eye ring.
Upper mandible blackish; lower mandible corn-yellow at base, blackish at tip. Tarsus blackish brown, toes darker.
Juvenile: Tail feathers dark blackish gray with paler buffy to white edges. Rump and upper tail coverts pale buffy gray, irregularly streaked and spotted dusky. Ground color of back grayish buff; back feathers streaked black and rust. Scapulars grayish buff on inner webs, rust on outer webs. Primaries and secondaries dull blackish gray. Primaries with narrow white streak along shaft, secondaries with narrow dull rusty edge and dull buffy tips. Tertials with black centers and broad whitish tips; outer web of innermost tertial almost entirely white, of outer two tertials mostly bright rust. Greater coverts with blackish centers, rusty edges, and large white tips, forming conspicuous lower wing bar. Median coverts blackish with broad white tips, forming conspicuous upper wing bar. Nape light smoky gray.
Under tail coverts, vent, and belly dull gray-tinged whitish. Breast tinged buff. Flanks and sides of breast pale brown-buff, with dusky streaks. Throat light gray with faint dusky streaking. Crown dull brown with fine blackish streaks. Ear coverts soft smoky gray, separate from broad supercilium by darker eye line reaching from back of eye to side of nape. Supercilium palest above lore; lore gray with variable dusky or dull reddish spotting. Very narrow whitish eye ring.
Upper mandible blackish; lower mandible dull yellow at base, blackish at tip. Tarsus dark pinkish brown, toes darker.
Length 134-152 mm (5.3-6.0 inches)
Wing chord 70-82 mm (2.8-3.2 inches)
Tail 64-73 mm (2.5-2.8 inches)
W:T 1.15
Mass 14-27 grams
