Distinguishing females of capuchino seedeaters: call repertoires provide evidence for species-level diagnosis

Reliable identification of cryptic Neotropical capuchino seedeater females remains as a recurrent and non-trivial issue in field ornithology. Even in the hand, capuchino females cannot be accurately diagnosed to the species level based solely on visual plumage examination, which may present a problem for future research on this group. During 10 years of field research on this group, we observed subtle vocal differences. We studied females of two parapatric species that may breed in syntopic upland grassland areas in southern Brazil: Tawny-bellied Seedeater Sporophila hypoxantha and Black-bellied Seedeater Sporophila melanogaster. Our main aim was to measure dissimilarities between inter-specific and intersexual repertory calls. We found unequivocal inter-specific divergences in call type repertoires revealed by cluster analysis, and no intersexual differences in the co-specific repertoire calls. These combined results enhance the understanding about the role of repertoire calls on species-specific recognition and interbreeding isolation processes (assortative mating), and provide a way to overcome the problem of field identification of female capuchinos at the species level.