VOCAL AND OTHER BEHAVIOUR OF KENYAN BLACK-COLLARED BARBETS LYBIUS TORQUATUS

We describe 12 visual and six acoustical displays of Black-collared Barbets, all associated with interactions of these sexually monomorphic barbets in greeting ceremonies and in antiphonal duets. Certain of the displays, e. g., bill directing, smooth posture and chatter calls largely are associated with multiple-barbet interactions and greeting ceremonies involving more than two barbets, and seem to represent purely agonistic displays. Other displays, most notably the bobbing and floating flight displays, and the tyaw call, are associated with preduet greeting ceremonies involving the presumed pair. In every case duets were performed by a presumed pair, following a greeting ceremony and visual displays accompany the duetting, which usually becomes precisely synchronized after the initial few notes. Four to 17 notes of each of two types, a usually lower pitched, short and mainly double type A note that introduces most duets, and a higher pitched, usually single, clear type B note that often terminates the duet. Variation in the notes and in their tempos within duets suggests no clearly defined temporal indicators for achieving, maintaining, and concluding the duets. The A and B notes cannot yet be assigned to one or other sex and similarity in form and development of the notes, from notes of greeting ceremonies, suggests the possibility that under some circumstances a bird of one sex may be able to deliver notes of either type. The duets are delivered from singing posts within the group's (or pair's) territory and usually only one duet is uttered from a site before the birds shift to another singing post. The duetting is compared with that of other barbets and appears to be among the best synchronized and most precise in the family. Comparisons with non-barbet duetting species are difficult because of the special habits and ecology of the barbets and uncertainty as to the sexual rôle of the duetters.