Song Repertoires and Song Sharing by American Redstarts

We studied the extent to which male American Redstarts (Setoph- aga ruticilla) share songs in their repertoires. Examining samples of songs from three locations in New Brunswick, Canada, we found significant heterogeneity the frequencies of the different songs across the locations. The extent to which neighbors shared songs related to increasing repertoire size (mean 4.4 songs/adult male). In the relatively larger sample at St. Andrews, neighboring adult males shared significantly more song types (P < 0.05) than did adult males chosen at random. However, this result applied only to individuals with intermediate-sized repertoires (four songs). Subadult males at St. Andrews shared as much with neighboring adult males as did adult males among themselves. In the small, island population at Back Bay, adult males shared noticeably more songs than St. Andrews. We attribute the difference in degree of song sharing to demographic aspects, including patterns of settlement, interacting with tendencies to copy songs. Therefore, any so-called "dialects" in songs of American Redstarts seem more "epiphenomena" resulting from competiton between males rather than as indi- cations of local adaptations of