Song structure and variability in the Black-headed Bunting (Emberiza melanocephala)

Abstract

Fighting and flirting are the main evolutionary forces behind the development of bird song and both contribute to different song characteristics. By comparison of vocalisations throughout bird taxa, we can help to reconstruct the evolutionary history of the song. In this study, we provide the first detailed analysis of song structure and song type variability in the Black-headed Bunting (Emberiza melanocephala). We quantify the fine structural characteristics of the song and describe the song and syllable repertoire size. Further, we describe intraindividual song variability over time and interindividual song variability over space, and we explore whether this species uses syntactic rules to create songs. Our analyses reveal that the Black-headed Bunting has a short yet rather complex song and that the syllable pool is extensive. Its song is constructed of three parts that differ in both complexity and rhythm, suggesting the use of syntactic rules in constructing a song. The male song is typically built of 9–13 syllables, with 7–12 that are non-repetitive. Each male sings only one stereotyped song, which remains identical throughout the male’s lifespan, providing evidence for age-limited song learning. Songs are individually distinct, suggesting the importance of song in individual recognition of males. Two spatial levels of song variation in the Black-headed Bunting are shown. On a microgeographical level, relatively small song neighbourhoods are formed with a handful of birds singing the same song type. On a macrogeographical level, dialects can be distinguished by the end part of a song. The most striking feature of the male Black-headed Bunting song is the immense variability of song types. Typically, only a small number of males shared the same song type, and males with unique song types occurred frequently as well. The high song complexity and single-song repertoire found in the Black-headed Bunting could reflect a high level of polygyny and a low level of parental care, therefore pointing to strong intersexual selection on the male song.