The scarlet rosefinch Carpodacus erythrinus populates large areas of the Palearctic zone. Beginning more than 30 years ago, the species expanded from its population centre in Asia and Eastern Europe to Northern and Western Europe. New breeding populations were thereby established, not only in suitable environments on the Baltic coast, but also along the big rivers (Vistula, Warta, Odra) and in the Central European inland area (for example The Alps, Bohemian Forest and Ore Mountains). While the process of expansion is well documented, we have very little information about the origin of the founder birds. During the last 15 years, the songs of more than 800 individual scarlet rosefinches (the whole of the five subspecies) were recorded. The spectrographic analysis shows that two different song forms are used by the males:
- the so-called short song which consists of 4-6 notes and varies in pattern and arrangement of the notes between individuals;
- the so-called long song which contains at least 9 notes and has a more or less homogenous structure in the whole area of the recent distribution of the species.
An analysis of the different types of the short song shows an increase of variation from the final to the initial notes. The final note is used for the description of song types, which can be divided into sub-types using other notes. The basic structure of the short song is identical for all sub-species. While in the Siberian, Middle Asian and Caucasian breeding areas we found that the birds prefer only certain types of notes, in the small isolated Central European micro-populations dialect songs emerged. Dialect songs were probably established by founders of the local breeding population. During the stabilization of the micro-population and with the increase in the number of individuals, a uniformity of song type takes place. Each population is characterized by one dominant song type or dialect. It can be assumed that the dialect is a learned marker by a micro-population.