A sweet whistled song, fee-bee with the second note lower than the first, similar to the whistles of many other chickadees. Mountain Chickadees sometimes sing more than one fee and/or more than one bee notes as well. Though they sound quite similar to Black-capped Chickadees, research has shown that the two species pay little attention to each other’s calls. You’ll mainly hear this song in summer.
Chickadees are extremely vocal. The most famous call is the one that gave the birds their name, a lively chick-a-dee used while mobbing predators, chasing rivals, singing, and staying in contact with a flock. They often repeat parts of the call, particularly the dee, and research on Black-capped Chickadees has suggested chickadees do this to emphasize the threat from a predator. Among their other calls is a burbling, half-swallowed gargle exchanged when two individuals face off or between mates.
Females and large nestlings sometimes hiss and slap the inside of their nest cavity if an animal disturbs them. The display mimics the sound and actions of a snake, and it’s thought to be an attempt to scare off predators.