Dialects in a Call Associated with Pair Interactions in the Black-Capped Chickadee

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Abstract
Calls of black-capped chickadees (Parus atricapillus) occurring during intrapair interactions were studied at 3 sites in southeastern Wisconsin [USA]. These vocalizations were given by both sexes in early phases of courtship and by males during copulation, and they also occurred later in the breeding season. The ending of this call exhibited a dialect pattern, being very different at 2 sites 22 km apart. Playback experiments showed that males responded more strongly to their own dialect than to the foreign one. Hand-raised birds that heard no chickadees other than their siblings after .apprx. 14 days of age produced aberrant calls, suggesting that learning is involved in the acquisition of these vocalizations. This is the first report of microgeographic variation in an avian vocalization associated only with intrapair associations and not involved with male-male interactions, as in the case with song.