Extraordinary variation in a simple song: No geographical patterns in initial phrase variation of the Yellowhammer, a passerine with pronounced dialectsAbstract

Geographical variation of birdsong is used to study various topics from cultural evolution to mechanisms responsible for reproductive barriers or song acquisition. In species with pronounced dialects, however, patterns of variation in non-dialect parts of the song are usually overlooked. We focused on the individually variable initial phrase of the song of the Yellowhammer (Emberiza citrinella), a common Palearctic passerine which became a model species for dialect research. We used a quantitative method to compare the similarity of initial phrases from the repertoires of 237 males recorded at different spatial scales in a central European country covering all main dialect types. We hypothesized that patterns of initial phrase sharing and/or phrase similarity are affected by dialect boundaries and geographical proximity (i.e. that birds from the same dialect regions use more similar phrases or share them more often). Contrary to our expectations, initial phrase variation seems unrelated to dialects, as we did not find higher similarity either among recordings from the same dialect areas or among those from the same locality. Interestingly, despite the immense variability of phrase types detected (only 16% of 368 detected initial phrase types were shared between at least 2 males), a relatively high proportion of males (45%) was involved in sharing, and males using the same initial phrase were located anywhere from tens of meters to hundreds of kilometers apart. The patterns of variation suggest that precise copying during song learning as well as improvisation play important roles in forming individual repertoires in the Yellowhammer. Our data also confirm previous indications that the repertoires of Yellowhammer males (i.e. the composition of initial phrases) are individually unique and temporally stable. This makes the species a good candidate for individual acoustic monitoring, useful for detailed population or behavioral studies without the need for physical capture and marking of males.