Geographic variation in the occurrence of song types in Nuthatch Sitta europaea populations

Abstract

The frequency of occurrence of song types of Nuthatches Sitta europaea was examined in nine study areas in northern Belgium. Birds from different areas did not differ consistently in the use of five distinct song types, and similarity in the occurrence of song types was not related to geographic distance, except that one song type, “Ud”, was almost wholly absent from four areas in the northeast of the investigated area. In the remaining areas, the frequency of occurrence of this song type varied from 10% to 20%. This presence/absence pattern appears to be stable between years. I suggest that the birds from the four areas lacking “Ud” were descended from a formerly small and highly isolated population near Antwerp, where the song may have been lost through a founder effect. Birds in areas with and without “Ud” did not differ in their response level to playback of this song, except that those in areas without “Ud” were incapable of song matching.