Solid black cap and bib, white cheeks, unstreaked greenish gray back, buffy flanks and crissum, dark grayish wings and tail. Pale edgings on the wing coverts and flight feathers. Bill black; legs and toes bluish gray, iris dark brown. Wings rounded; tail long. Sexes alike in plumage, with males slightly longer than females in wing and tail. Length 12.3 to 14.6 cm; mass 10-14 grams (Smith 1993).
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.
The amount of white on the outer edge of the greater coverts is the best character for distinguishing Parus atricapillus and P. carolinensis in the field, but birds in the contact zone may not be identified with certainty (Robbins 1989).
Western Hemisphere Range
Deciduous and mixed deciduous/coniferous woodland, open woods and parks, willow thickets, and cottonwood groves. Also disturbed areas such as old fields or suburban areas. Generally more common near edges of wooded areas (Smith 1993).
During winter 50% animal (mostly insects and spiders) and 50% plant (primarily seeds and berries). During breeding season 80-90% animal (largely caterpillars), the rest seeds and fruits (Smith 1993).
Nests in cavities. Natural sites typically in trees, especially dead snags or rotten branches, sometimes old woodpecker holes or even in bird boxes. Nest built exclusively by female. Most common clutch size 6 to 8 eggs (Smith 1993). Near Fortine, the earliest eggs were on May 26 and the earliest young were on June 24. Statewide, egg records are from May 12 to July 28.