American Tree Sparrow
Spizella arborea

Migratory Status: Short-distance migrant

PIF Population Estimate: 30 000 000

Percent of western hemisphere population breeding in boreal forest: <25%

BAM Effective Detection Radius (m) : 94.1

PIF Maximum Detection Distance (m) : 200

Canadian BBS Population trend: Insufficient data

Life History

The American Tree Sparrow is a rare sight for most birding enthusiasts during the breeding season, since much of the breeding range is in the roadless and inaccessible north. Breeding in open, shrubby habitats near bogs or lakes in the boreal forest, as well as in the taiga and open tundra, this species generally relies on thickets of willow (Salix spp.), birch (Betula spp.), or alder (Alnus spp.) for nesting and foraging. Therefore, this species is more frequently observed during the winter months at local backyard bird feeders or during migration.

The American Tree Sparrow in breeding plumage is distinctive and easily distinguished from other Spizella sparrows by their gray head, face and neck, rusty-coloured cap and eye-stripe, and an unstreaked gray breast with a dark central spot. Other physical features that can be used to help identify this species in the field are the two distinctive white wing-bars, streaked upperparts, and two-toned bill.

The breeding range of American Tree Sparrows covers most of Alaska, and extends eastward across the Yukon and Northwest Territories, to northern Quebec and Labrador. The breeding range in Canada also encompasses the northern portions of British Columbia, Manitoba, Saskatchewan, and Ontario. All populations are migratory and during the winter, the American Tree Sparrow can be found residing anywhere from northern Arizona, New Mexico, Texas, and South Carolina northward into the southern regions of Canada.

The American Tree Sparrow has a variable diet and will feed on seeds, insects and other invertebrates, as well as fruits and berries. Foraging predominately on the ground and in bushes, it will scratch for seeds and glean insects off branches and leaves. In the summer months of June and July, it feeds almost exclusively on insects, whereas during the winter seeds and catkins become a much larger part of its diet. When fresh snow covers fallen seeds, the American Tree Sparrow is known to beat its wings against exposed weeds and grasses, causing new seeds to fall on the snow, which it then collects.

Only male American Tree Sparrows sing and, although variations in song types exist, each male will adopt and use one song type exclusively to defend their territories and attract mates in the breeding season. Because this species breeds so far north, very little is known about how it disperses and whether males return to their natal areas. However, local dialects of its song exist, and thus, it is likely that breeding site fidelity is high. During fall migration and the winter season, this species becomes less territorial and will often associate in single and mixed species foraging and roosting flocks.

Reference(s)

Ashenhurst, A. R., and S. J. Hannon. 2008. Effects of seismic lines on the abundance of breeding birds in Kendall Island Bird Sanctuary, Northwest Territories, Canada, Arctic, 61(2):190-198.

Dauwe, T., L. Bervoets, R. Blust, R. Pinxten, and M. Eens. 2000. Can excrement and feathers of nestling songbirds be used as biomonitors for heavy metal pollution?, Archives of Environmental Contamination and Toxicology, 39:541-546.

Koch, I., J. V. Mace, and K. J. Reimer. 2005. Arsenic speciation in terrestrial birds from Yellowknife, Northwest Territories, Canada: The unexpected finding of Arsenobetaine, Environmental Toxicology and Chemistry, 24(6):1468-1474.

Naugler, C. T. 1993. American Tree Sparrow (Spizella arborea), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/037