The songs of oscine birds, given their cultural inheritance, can readily diverge, which can foster assortative mating and ultimately reproductive isolation. The species complex of Dark-eyed Juncos (Junco hyemalis) consists of at least six distinct subspecies and represents an ideal system for studying divergence in mating signals owing to its recent, rapid radiation throughout North America since the last glaciation (<15,000 yrs). Each subspecies of Dark-eyed Junco is characterized by distinct plumage and morphological characteristics, but divergence among the subspecies in song and the role of song as a potential isolating mechanism remains to be rigorously tested. In this study, I compared territorial responses of male juncos in Virginia to playback of locally recorded songs and songs recorded from a different population and subspecies in California. Males responded aggressively to playbacks from both populations, but they approached more rapidly and closely, and performed more flyovers when responding to local song types. While these results suggest that male juncos can discriminate between songs of different populations, future work should investigate female preferences for local and foreign songs and also address more populations, particularly those located in active hybrid zones.