The chestnut-backed chickadee is curious about humans, and spends the postbreeding and winter seasons foraging noisily in mixed-species flocks. Unlike other parids (except for the mountain chickadee), it forages high in the canopies of tall conifers. This species is the smallest chickadee in North America. One of the 3 “brown-backed” species (along with boreal and gray-headed), its nominate subspecies is the most richly colored parid. Polytypic. Length 4.8".
The chestnut color of the back is unique, but it varies in intensity. The cap is dark brown, shading to black at its lower edge from the bill through the eye; the cheek is white; the bib is black; the back and rump are rufous; the greater wing coverts are edged white; the breast and belly are whitish; the sides and flanks are bright rufous or dull brown, depending upon the subspecies; the tail is brownish gray.
Three subspecies. The widely distributed rufescens is the most colorful, with a rich chestnut back, bright white edgings on the greater wing coverts, and extensively bright rufous flanks. The other 2 subspecies are restricted to coastal California; they differ notably on the underparts. In Marin County, the neglectus has reduced, pale chestnut flanks that do not contrast conspicuously with the whitish breast and belly; barlowi, found from San Francisco to northern Santa Barbara County, has grayish flanks, tinged with olive brown.
The boreal chickadee also has a dark brown cap and rich brown sides and flanks, but it has predominantly grayish cheeks, lacks a rufous tint on the back and rump, and shows no white wing edgings.
Call: a hoarse, high-pitched, rapid sik-zee-zee or just zee-zee; also a characteristic sharp chek-chek. Song: no whistled song is known.
Status and Distribution
Common. Year-round: Coniferous forests, especially of Douglas fir, and mixed and deciduous woodlands. Dispersal: postbreeding movements have been noted to higher elevations in British Columbia and to lower elevations in Oregon. Vagrant: wanders irregularly inland as far as southwestern Alberta and casually south of its usual range to southern California.
Its range has expanded southward and eastward in recent decades from humid coastal regions to the drier eastern San Francisco Bay area and the forested Sierra Nevada in California. Numbers appear to be stable in the northern portion of the range, but recent declines in the interior expansion area have raised conservation concerns.
—From the National Geographic book Complete Birds of North America, 2006