Travelling across subspecies borders: songs and calls of the Common Chaffinch Fringilla coelebs in the contact zones and adjoining areas of southern Russia

Capsule: Although many acoustic signals of Common Chaffinches Fringilla coelebs, including both songs and rain calls, are widespread across its distribution range, the boundaries between subspecies place formidable obstacles to the spread of vocal patterns. Aims: To investigate the diversity of song types and song structure of rain calls in the contact zone between the Caucasian and Crimean subspecies of Chaffinches in the north-western Caucasus, as well as between the nominate and Caucasian subspecies in the northern Ciscaucasia (south of European Russia). Methods: In total, the songs and rain calls of more than 300 males were recorded in 10 different locations in the Crimea, Caucasus, and Ciscaucasia. For comparison with more remote areas, we used our recording of Chaffinches from the Voronezh region and the city of Moscow. Results: The song repertoires of Chaffinches in the Crimea and on the Abrau Peninsula (Black Sea basin) were very different despite being less than 100 km apart. In contrast, the repertoire of the Abrau population had much in common with the more distant (270-300 km) populations of the Caucasus and Ciscaucasia. The rain calls of Chaffinches on the Abrau had a unique two-syllable structure. On a sonogram, both of these types of sounds look very similar to the single-element calls of Caucasian and Crimean Chaffinches, but are significantly different in their frequency and temporal characteristics. Conclusion: Zones of contact between Chaffinch subspecies appear to be a kind of filter that make it difficult to spread vocal patterns from the range of one subspecies to the range of another.