The ontogeny and function of duet codes in territory dynamics of the riverside wren

Abstract

In some species of songbirds, both females and males sing and coordinate their vocalizations to create highly complex joint performances known as duets. Additionally, in some of these species, pair mates combine their individual vocalizations following consistent pair-specific associations, known as duet codes. Investigating how birds create their individual and pair repertoires and how duet codes are used in within- and between-pair interactions is essential for understanding how each sex benefits from learning this complex behaviour and to characterize the nature of the selective mechanisms that promoted the evolution of this joint signaling system. This thesis focuses on a population of riverside wrens, Cantorchilus semibadius, as a means to investigate the song learning strategies of each sex, to elucidate the functions of duet codes in intra- and inter-sexual interactions, and to measure the cooperative nature of the defence strategy of both sexes. To achieve these goals I conducted a long-term study and a series of playback experiments. I found an unusually high turnover rate compared to other duetting species. I also found that individual and pair repertoires are considerably stable over time and are highly shared across the population, which suggests that individuals create their repertoires as juveniles and settle nearby their tutors, as vacancies arise frequently. During territory defence, partners maintained a close distance with each other, both sexes approached closely to both simulated intruders, and both sexes matched the songs of same-sex rivals at similar rates but mostly sung in coordination with their partner. This indicates females and males benefit from displaying a strong partnership and perform a joint defence against rivals. My thesis suggests duetting is a cooperative behaviour and the function of duet codes might be mostly related to within-pair interactions in the riverside wrens.