Lybius

Abstract: -Our East African studies have focused on the sociality, duetting and intraand interspecific systematics of barbets (Capitonidae). The Afrotropical barbets include 14 duetting, social species and 22 non-duetters, both social and non-social. In this review of them, comparisons are broadly conducted, but centered about the ground barbets (Trachyphonus) and some species of Lybius. The sexually dichromatic Red and Yellow Barbet (T. erythrocephalus) occurs in pairs and in social groups; duetting is by the pair, or mainly by the primary pair of a group. Within groups, secondary adults and young may join in part of the duet but their roles are limited by the dominance of the primary pair. The sexual songs are not very different. Subspecies of erythrocephalus differ little morphologically except in color tone and size. Darnaud's Barbet (T. darnaudii) is sexually monomorphic with races morphologically somewhat divergent. Sexual duetting roles are distinctive, and in groups the primary pair actively prevents duetting of secondary adults or young birds. Removal of a duetter leads to instant replacement from within the group, another bird assuming the duet role of the lost bird. In the Red-faced Barbet (Lybius rubrifacies), the Black-collared Barbet (L. torquatus) and the Black-billed Barbet (L. guifsobalito) the sexes are alike, pairs and social groups occur, and duetting is by the primary pair, with distinct sexual duet roles, following a greeting ceremony in which other individuals may take part. Secondary "pairs" occur in some groups; these may duet when apart from the primary pair, but not in the presence of the latter. Allopatric torquatus and guifsobalito show no or modest geographic variation and have similar though distinctive duets. Lybius rubrifacies shows no morphological geographic variation, and marginally overlaps torquatus; its duet markedly differs from that of torquatus. The duet songs, whatever the degree of genetic control, are species-specific. Only paired duetting birds hold territories. Systematic comparison and studies of sociality and duetting in Afrotropical barbets suggest that the nature of their social systems and their duets, where these exist, has affected their speciation, and vice