Microgeographic Variation in Songs of Splendid Sunbirds Nectarinia Coccinigaster : Population Phenetics, Habitats, and Song Dialects

Abstract

Songs of Splendid Sunbirds at Cape Coast University, Ghana, were recorded and the audiospectrograms analyzed by multivariate statistical techniques. Neighboring birds usually had similar but nonidentical songs. Groups and subgroups of neighbors occurred at distances up to 7 km. Several birds had songs intermediate in structure between those of the main groups, and a few had songs unlike their neighbors. Song differences measured by phenetic distances are significantly correlated with microgeographic distances between the birds, at distances up to 1-2 km. The variation in song is described in terms of dialects and in terms of behavioral variation with microgeographic distance. The dialect areas were less than 1 km2 and involved from 5 (probably an underestimate) to 14 individual males. The local microgeographic scale of song variation agrees with that reported for other populations in Ghana, but variation in space is not as grouped into discrete dialects as described by GRIMES (1974). Birds with similar songs did not consistently occur in similar habitats, except when the birds were neighbors in a common patch of habitat. No song differences were associated with the presence of different coexisting species of sunbirds. Birds at distances of 10 to 400 km were little more divergent in song than birds within the 4 km2 area of the main study site. No geographic trends in song were found along more than 100 km of the coastal plain of Ghana, and no consistent differences were found between coastal and inland populations. Similarities among the songs of neighboring birds, differences between neighborhoods, and the uniform size of the song "dialects" are tentatively explained in terms of social adaptation rather than habitat adaptation.