Dialect discrimination by male orange-tufted sunbirds (Nectarinia osea): Reactions to own vs. neighbor dialects

Abstract

Male orange-tufted sunbirds (Nectarinia osea) exhibit distinct song dialects throughout Israel. Recently, two distinct local dialects with a sharp boundary were discovered in a small (1.5 km2) urban neighborhood densely inhabited by 63 territorial sunbird pairs. We conducted playback experiments to determine song dialect discrimination capability by sunbird males in this neighborhood. Males of both dialects responded significantly more strongly to playback of their own dialect than to that of the adjacent dialect. In spite of the extreme proximity between the two dialect areas, we found no effect of distance to the neighboring dialect on the intensity of any the behavioral responses. We suggest that due to the complex acoustic properties of this urban neighborhood, sunbirds are extremely limited in the number of neighboring males they can assess to establish what the local song is. A stronger response to one's own dialect is therefore expected, and we discuss how local dialects could be maintained via this mechanism regardless of the very small distances between territories and dialect populations.