Divergent tunes: exploring dialects in Great Reed Warbler song pattern

Abstract In most songbirds, there is geographic variability in their songs, and for some of these species, populations display unique vocal characteristics that can be used to identify the origin of individual birds, i.e., dialects. Although studies indicate the significant role of dialects in bird vocal behaviour, the majority of species remain largely unexplored in this regard. In this paper, we investigate whether dialects occur in the vocal behaviour of the Great Reed Warbler ( Acrocephalus arundinaceus )—a model species in studies of birdsong and sexual selection. In this study, we analyze the vocal behaviour of ten Great Reed Warbler populations, ranging in distance from 6 to 410 km. We test the hypotheses that (i) populations of the Great Reed Warbler differ in dialects and (ii) differences in dialects between populations increase with the distance that separates their breeding grounds. The results of our research confirmed both our hypotheses. Each population had characteristic whistles or their specific combinations, allowing males to be assigned to the population they originated from based on their song. We also demonstrated that the between-population variation in syllable repertoire increases with the distance between populations. The greatest similarities in the repertoire composition occur among populations separated by less than 50 km which may result from individuals moving between closely located populations, thereby sharing vocalisations. As the distance between populations increases, the likelihood of individual migration decreases, which in turn favors the emergence of specific and distinct elements of the song for each population.