Communication with Shared Song Themes in Tufted Titmice

Individual Tufted Titmice (Parus bicolor) sing 8-12 song themes. Most or all themes in an individual's repertoire are shared with neighbors, although slight but consistent differences often separate neighbors' performances of a particular theme. Birds first begin to sing recognizable themes while still juveniles on their parents' territory. Established territorial residents can modify their themes slightly from year to year to achieve a closer similarity to neighbors' themes. Neighbors matched themes during concurrent singing more often than would be expected at random. Furthermore, titmouse tended to begin singing in response to a neighbor, particularly if it could match the theme. Playbacks of recorded song also evoked matched singing in response. Playbacks of strangers' songs, recorded 3 km away, evoked a less intense response than did playbacks of neighbor's songs, but an attempt to demonstrate individual recognition of a neighbor's shared themes failed. Evidently, the advantages of coordinated singing by opponents with shared themes outweigh any advantages of individual recognition of neighbors with distinctive songs.