The songs of 175 yellowhammer Emberiza citrinella males were recorded in an area of 10 km2 in 1977-1981, 1983 and 1996. Each male had a repertoire of 1-3 song types (mean: 2.1), being categorized mainly by the first part of the song, which is a repetition of a sound pattern (the a-element). Comparisons of population repertoires of a-elements between years showed that a-elements had an annual survival rate of about 95%.
In a computer simulation all 373 a-elements from the study years (the summed male repertoires) were pooled (distributed among 80 a-element types). From this pool samples of a-elements were drawn, corresponding to the sample size of each study year, and the number of types per year and shared types between years were calculated. Both measures fitted well to the actual findings in the population.
Thus the recorded songs might have been drawn from a stable song type population, suggesting that yellowhammer song elements are transmitted culturally through a considerable number of generations.
The mechanisms which might be responsible for the slow degree of cultural evolution in yellowhammer songs are discussed.