Bird Sighting: American Tree Sparrow
American Tree Sparrows (Spizella arborea) are large for sparrows, approximately 6 inches in length and have a long tail. Both sexes look alike. The upper mandible, legs, and feet are dark; the lower mandible is predominantly yellow. The crown and eye stripe are rufous (reddish brown) in color while the brow, cheeks, throat, and nape are gray. The belly is also gray while the flanks show a buff wash. The back is rusty brown with dark streaks. Extending from the bend of the wing into the gray breast is a distinctive rufous-colored comma. The outermost outer tail feathers are pale and dusky with a thin outer vane approaching white. However, the most characteristic markings of the Tree Sparrow are the unmistakable dark brown spot in the center of the breast, and the frosty edges of the wings and tail. It is by these markings that observers may quickly identify this species.
American Tree Sparrows range across a vast expanse of North America breeding from Alaska, northern Saskatchewan, northern Manitoba, and northern Quebec south to northern British Columbia, central Quebec, and Newfoundland. They will overwinter across most of the United States as far south as California, Arkansas, and the Carolinas. As a result, they are a common sight at winter feeders. Precise numbers are difficult to determine, but if the total breeding area (approximately 247 million acres) is taken into account, it is possible that there are between 10 and 20 million pairs breeding across North America.
Unlike northern finches such as crossbills or Pine Siskins, Tree Sparrow winter feeder numbers seem to depend on weather, not food supply. In fact, they are less numerous in mild winters. With sufficient calorie intake, they can tolerate subzero temperatures and are capable of wintering in open country where snow does not entirely bury the weeds and grasses. Thus, their winter habitats include weedy fields, hedgerows, farmland, brushy woodland edges, marshes, thickets, and residential areas. They will often forage the snow-covered landscape in large flocks.
The Tree Sparrow's song consists of a series of thin, high, whistled notes followed by a sweet, rapid warble. They also exhibit a winter feeding call -- a hard, shrill "tseet" song.
In the summer and for breeding, American Tree Sparrows prefer to inhabit willow and birch thickets and other scrubby areas near the tree line, usually marked by conifers. Nesting sites are on or near the ground, often in a tussock of grass at the base of a shrub. The nest itself is bulky and well-insulated – an open cup of moss, grasses, shreds of bark and twigs. It is lined with fine grass and feathers. The female will lay 4 to 6 pale blue eggs, speckled with reddish brown. Juveniles are similar in appearance to adults, but with some streaks on the crown, nape, and breast.
Despite their name, American Tree Sparrows principally forage on the ground or in low shrubs. During the summer, their diet consists of nearly 100% animal matter (mostly insects). In the winter they switch over to an all-seed and berry diet. Favorites include grass and weed seeds such as goldenrod, aster, and crabgrass. But Sparrows are far from picky eaters and enjoy many feeder offerings.
Spotting and Attracting American Tree Sparrows:
There are several species similar to the American Tree Sparrow. The Chipping Sparrow is most similar, but is smaller. It has a black (not rufous) stripe through the eye and a brown crown with faint streaks in winter. The Field Sparrow has a pink bill and a distinct eye ring. The Lark Sparrow has a bold face pattern and white on the outer tail feathers. All three of these species lack the distinctive dark central chest spot.
Do not be discouraged by all this similarity, though. The migration times of these birds do not exactly coincide. For example, American Tree Sparrows typically arrive in late October, and within a week, Chipping Sparrows depart. In late March, American Tree Sparrows depart within a week or so of the Chipping Sparrow's arrival. Thus, it is unlikely that you will see the two species in the same location at the same time.
The most fun about inviting American Tree Sparrows to your back yard is watching them forage. For this, the best enticement is a ground feeder which will raise seed above the snow, but still offer a place to scratch and hop about. Try also to provide low cover nearby. Deciduous shrubs like Forsythia and Burning Bush are good choices. After the holidays, you may want to leave your old Christmas tree out in the yard as a seasonal bird shelter.
Seed choices are easy since Tree Sparrows enjoy the same foods as many finches. Offer a mix of niger, sunflower chips and classic bird seed. And as always, a reliable winter water supply will be greatly appreciated by your birds.