VOCALIZATIONS AND OTHER STIMULI THAT ELICIT GAPING IN NESTLING BLACK-CAPPED CHICKADEES (PARUS-ATRICAPILLUS)

Parental vocalizations that influence the feeding process of nestling passerines have not been well studied. Vocalizations of Black-capped C hickadees (Parus atricapillus) were analyzed by audio and video record ings within the nesting cavity. One vocalization, the ''squawk,'' stim ulated gaping in nestlings during the feeding process. Parents gave sq uawks most during the first 48 h posthatching when nestlings were freq uently unresponsive to vocalizations and equally or more responsive to vibratory and other stimuli. Contrary to reports about other species, spontaneous gaping did not occur frequently at any age. Within the fi rst 48 h posthatching, however, gapes frequently occurred to ''irrelev ant'' stimuli. As nestlings aged, they gaped more frequently to stimul i directly associated with feeding, such as to squawks at three to sev en days of age and to the parents' arrival at older ages. The parents' vocalization plays an important role in coupling the nestlings' gapin g response with the appropriate situation, especially during the first days posthatching when nestling responses are coarsely tuned to appro priate stimuli.