Figure 1. Main song classes of male European starlings, based on field observations of more than 300 birds.

Class-I whistles (top row) are present in the repertoire of all or most males, with the same characteristics and variation range. They are subdivided into 4 main types or themes (from left to right): inflection theme, theme with harmonics, rhythmic theme and simple theme. Class-II songs (middle rows) are individual whistles that characterize one bird in its colony. Bottom row shows parts of the class-III song (also called warbling) including 1-2 motifs (which are the basic acoustic and perceptual units of warbling [5], [16]). Modified from Hausberger [7].