Vocal and Behavioral Responses of Brown-Headed Cowbirds to Flight Whistles from Different Dialects

We examined the vocal and behavioral responses of free-living male Brownheaded Cowbirds (Molothrus ater) to playbacks of flight whistles (FWs) from local, nearforeign, and distant-foreign dialects. Full, partial, and reverse FWs were broadcast to solitary males. Test males responded with their own FWs and approached playbacks of FWs significantly more than playbacks of control heterospecific vocalizations. This suggests that all three dialects were recognized as conspecific. The strongest responses were elicited by playbacks of local FWs, and there was little behavioral evidence that males distinguished between the near-foreign and distant-foreign dialects. Males responded to playbacks of partial or complete local FWs primarily with the next or missing part of the FW. That is, they avoided matching the playback. The FW responses to playbacks of near-foreign and distantforeign FWs were not consistent. Males presumably use matching-avoidance within a FW dialect to initiate social interactions with particular conspecific males.