Variation in quantitative properties of song among European populations ofreed bunting (Emberiza schoeniclus) with respect to bill morphology

We analysed the geographical variation in quantitative song properties amon g reed bunting (Emberiza schoeniclus ssp.) populations belonging to two sub species groups with different bill morphologies: large and curved bill (nam ely E. s. intermedia and E. s. witherbyi, in southern Europe) and thin and conical bill (E. s. schoeniclus, in northern Europe). We collected song rec ordings from 11 European populations of the two subspecies groups and measu red song properties of 116 males. We found significant differences among po pulations despite a high degree of individual variation. Populations with s imilar morphology were more homogeneous in song characters, despite geograp hical distances between them. The two subspecies groups differed mainly in the number of different syllable types used in a song, with the songs of th e southern group having higher syllabic complexity. Cluster analysis and ma trix correlation tests showed an association between song variation and mor phological variation. The populations morphologically belonging to E. s. sc hoeniclus along the contact zone of the breeding distributions had song cha racters similar to southern populations and possibly represent a "hybrid" z one, which is not evidenced by morphological or recent genetic analyses. Th is may be due to song being learned socially, populations mixing in winter and, along the contact zone, populations of different subspecies groups oft en breeding a few kilometres apart. The generally high degree of variation in song among populations can be a consequence of the relative isolation of the breeding populations, which are restricted to uncommon and fragmented habitats, along with the rapid cultural evolution of song in this species.