Song-type sharing between male Rock Wrens in northern Colorado

We examined song-type sharing and song-type co-occurrence among broadcast songs in a migratory population of a songbird with large and highly variable repertoire sizes, the Rock Wren (<em>Salpinctes obsoletus</em>). Large song-type repertoires may offer a competitive advantage in intrasexual competition and provide opportunities for varied patterns of song-type sharing. We found that Rock Wrens in one population showed a general tendency to overproduce highly shared, i.e., popular, songs, and males with smaller repertoires sang more popular songs than males with larger repertoires. Song types with lower minimum frequencies and slower trill rates tended to be more popular, potentially enhancing song transmission. Using network analyses, we found non-random song sharing between pairs of males that does not seem to be mediated by location. Song-delivery rates of males were positively related to their song sharing with other males, and it is possible that both mediate male-male aggression or female preference. We also found that some pairs of song types co-occurred in birds’ repertoires more than others, but the song co-occurrence network was not clustered, raising questions about what factors drive song co-occurrence and repertoire composition. Taken together, our results suggest that song sharing and singing locally popular songs may play an important role in social communication. The results support the notion that having a larger repertoire allows a bird to sing both rare and popular song types and use rare or unique song types that can be used in assessment by rivals, more often than birds with smaller repertoires.