Experience affects immediate early gene expression in response to conspecific call notes in black-capped chickadees...

Black-capped chickadees (Poecile atricapillus) produce numerous vocalizations, including the acoustically complex chick-a-dee call that is composed of A, B, C, and D notes. D notes are longer in duration and lower in frequency than the other note types and contain information regarding flock and species identification. Adult wild-caught black-capped chickadees have been shown to have similar amounts of immediate early gene (IEG) expression following playback of vocalizations with harmonic-like acoustic structure, similar to D notes. Here we examined how different environmental experiences affect IEG response to conspecific D notes. We hand-reared black-capped chickadees under three conditions: (1) with adult conspecifics, (2) with adult heterospecific mountain chickadees, and (3) without adults. We presented all hand-reared birds and a control group of field-reared black-capped chickadees, with conspecific D notes and quantified IEG expression in the caudomedial mesopallium (CMM) and caudomedial nidopallium (NCM). We found that field-reared birds that heard normal D notes had a similar neural response as a group of field-reared birds that heard playback of reversed D notes. Field-reared birds that heard normal D notes also had a similar neural response as birds reared with adult conspecifics. Birds reared without adults had a significantly reduced IEG response, whereas the IEG expression in birds reared with heterospecifics was at intermediate levels between birds reared with conspecifics and birds reared without adults. Although acoustic characteristics have been shown to drive IEG expression, our results demonstrate that experience with adults or normal adult vocalizations is also an important factor.