Simultaneously vocalizing Asian barbets adopt different frequencies without coordinating temporal rhythms

Sound stream segregation is an important challenge faced by simultaneously vocalizing animals. Chorusing birds, for instance, coordinate vocal timing to minimize overlap. Alternatively, other birds may use frequency differences to segregate sound streams, and vocalizing at different frequencies may enable them to remain distinct from each other. Here, I show that conspecific Asian barbets vocalize at distinctly different peak frequencies from each other. Additionally, they also differ in repetition rate, as measured by the inter-phrase interval. However, conspecific individuals across species do not temporally coordinate with each other during vocal interactions, maintaining independent and highly stereotyped individual rhythms together with different peak frequencies. Frequency differences between individuals may facilitate sound stream segregation when calls overlap in time. I propose that frequency differences between conspecifics may be widespread among birds possessing stereotyped, repetitive calls such as those found in barbets. This may enable segregation of competing sound streams both during cooperative duets and competitive singing during territorial interactions.