Male and female Stripe-backed Wrens (Campylorhynchus nuchalis) have repertoires of learned, stereotyped calls that are specific to same-sex relatives in cooperatively breeding family groups. Consequently, they are potential cues for recognizing group membership and sex during social interactions. Here I describe the use of these calls for social communication in this species. Males call much more frequently than females within a group's territory, and dominant birds call more often than subordinates. In playback experiments, males responded to their own-group calls by producing matching call types, and called at relatively high rates following simulated territorial intrusions by neighboring birds. These vocalizations appear to function primarily in maintaining social bonds within a group and in recognizing group identity during interactions with other groups.