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

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 nondialect 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 ...