The Mountain Chickadee (Poecile gambeli) is a small songbird, a passerine bird in the tit family Paridae. Often, it is still placed in the genus Parus with most other tits, but mtDNA cytochrome b sequence data and morphology suggest that separating Poecile more adequately expresses these birds' relationships (Gill et al., 2005). The American Ornithologists' Union has been treating Poecile as distinct genus for some time already.

Adults of both sexes have a black cap joining a black postocular stripe behind distinctive white eyebrows. Their backs and flanks are gray and they have paler gray underparts; they have a short black bill, and a black bib. The typical adult wingspan is 7.5 inches (19 cm), and their overall length is 5.5 inches (14 cm).

Common inhabitants of the mountainous regions of the western United States, their range extends from the southern Yukon to California and western Texas. Although primarily nonmigratory, in the fall and winter Mountain Chickadees may extend their range into the lowlands typically inhabited by the similar Black-capped Chickadee.

They breed monogomously, producing 1 to 2 broods per year. Incubation by the female is 14 days. The young are altricial, and stay in the nest for 21 days while being fed by both parents.

Their primary diet is insects during the summer and breeding season; conifer seeds and other plant seeds are taken throughout the year. They cling to the undersides of branches and to tree trunks, searching for food in the bark or breaking seeds open by hammering them with their beaks.

Their call is a throaty chick-adee-adee-adee, while their song is a 3- or 4- note descending whistle fee-bee-bay or fee-bee-fee-bee. They travel in pairs or small groups, and may join multi-species feeding flocks after breeding season.

The specific name honors naturalist William Gambel.