Development of Early Vocalizations and the Chick‐a‐dee Call in the Black‐capped Chickadee, Parus atricapillus

The chick‐a‐dee call of the black‐capped chickadee ( Parus atricapillus ) is composed of discrete elements, or notes, that are combined to form hundreds of different calls. To investigate the development of this complex call, 12 families of color‐marked chickadees were observed and recorded in the wild. Vocalizations were monitored for 18 d in the nest and 14–18 d postfledging. Most vocalizations of nestlings and fledglings were associated with feeding. At hatching, vocalizations consisted of a structurally simple note type that became more complex and variable with age. Around 9–12 d, the development of the call occurred, when single notes became organized into a multiple‐note unit. Notes within the call differentiated into higher frequency, rapidly modulated initial note types and a lower frequency, moderately modulated terminal note type, features also present in adult chick‐a‐dee calls. Several adult‐like calls including chick‐a‐dee calls, fee‐bee songs, and a subsong‐like vocalization developed prior to fledgling dispersal. Based on resemblances of note structure and general call structure, the chick‐a‐dee call appeared to develop from calls of nestlings and fledglings, although not necessarily in a chronologically linear progression. Some features of the chick‐a‐dee call closely resembled features of older nestling and fledgling calls, while other features more closely resembled the sounds of very young nestlings. Vocal development in the chickadee is compared with song and call development in other species, and the possible significance of acoustic resemblances between chick‐a‐dee calls and the food‐associated calls of nestlings and fledglings is discussed.