By April, mountain bluebirds are returning to Colorado, having wintered on the Southern High Plains or in the Desert Southwest. The sky blue males are the first to arrive, searching for nest cavities which they use to attract a mate; those settling in the foothills, canyons and mountain valleys must compete with western bluebirds and violet-green swallows for those treasured sites.
Once the grayish females arrive, mountain bluebirds pair off and begin their nesting activities; while the males provide token assistance, the female takes charge of the nest construction, most often tucked within a tree cavity but sometimes in a rock crevice or a gap in an old cabin. Favoring open woodlands, mountain bluebirds may be found from the ponderosa parklands of the Colorado foothills to the krummholz at the alpine timberline; those that nest at lower elevations sometimes raise a second brood later in the summer.
Mountain bluebirds breed and summer in the mountain ranges of western North America, from Alaska to New Mexico. Like other bluebirds, they usually hunt from a perch, dropping to the ground to snare insects; they also snatch their prey in mid-air and mountain bluebirds often hover above their quarry before striking. During the colder months, all bluebird species supplement their diet with berries. Mountain bluebirds are especially nomadic in late summer and early autumn, regularly appearing on the Great Plains and, occaionally, in the eastern U.S.