Chestnut-backed Chickadees don’t have the clear-whistled fee-bee song that most other chickadees use. Instead it has a song, given rarely, that consists of a series of “gargle” calls.
The main call of the Chestnut-backed Chickadee is a high, thin, scratchy chick-a-dee, 1-1.5 seconds long. The number of dee notes is variable, but typically fewer than in the Black-capped Chickadee’s call. The Chestnut-backed Chickadee’s other common call is the gargle, a jumble of short clicks often dropping in pitch and ending on a longer note. The whole call lasts about a second. It’s typically used to defend territories or to signal aggression by birds in a flock.
Incubating adults and near-to-fledging nestlings hiss at intruders to the nest, accompanying this snake-like sound with a sharp slap of the wing against the walls of the nest cavity.