Smallest and relatively shortest-tailed of North American chickadees. Males: 105.0 mm to 120.5 mm. FeMales: 100.0 mm to 114.0 mm. Average mass for all 8.5 to 12.6. Cap, from forehead to hindneck extending to just below eyes, dark brown with slight grayish tinge becoming blackish through eyes bordered below by white cheek patch. Back to rump deep rufous-chestnut. A dark blackish-brown bib extends across malar region, chin, throat, and upper breast. Readily distinguished from other North American chickadees by the chestnut back and rump. Lacks a whistled song; rarely uses the Gargle call; has a particularly robust "chick-a-dee" call (Dahlsten et al. 2002).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
Found in humid coastal and interior forests from southeastern Alaska to southern California. Year-round resident throughout its range. Occurs within the densest coniferous forests, or along edges, where temperature is even and there is considerable shade (Dahlsten et al. 2002).
Insects and arthropods make up approximately 65% of the Chestnut-backed Chickadee's diet. Seeds and plant material make up the rest. During the winter, they forage in mixed-species flocks with other chickadees (Dahlsten et al. 2002).
Nests in tree cavities and readily colonizes available nest boxes. Eggs are ovate to short-ovate to long-ovate with great variation even within the same clutch. Smooth, white in color with few to many reddish to light-brown spots. Clutch size ranges 1 to 9 eggs (Dahlsten et al. 2002). Incubation has been observed June 5 and feeding of young on July 16. Egg dates are probably similar to those in Washington: April 7 to June 10.