Figure 1.

Spectrograms of (a) a segment of a song bout from an adult male starling, with the temporal boundaries of motifs indicated by horizontal bars above, (b) the last motif in the song above (top) and two variants recorded in other songs, and (c) variants of a motif by a different singer. Variants may have differences in note composition [e.g., (b) top vs bottom] as well as differences in note features [e.g., compare duration of trilled note in the last half of (c) motifs]. The range of variation in motif structure shown here is typical, from slight differences in duration and timing of the component notes (c) to having less than 50% of their notes in common [(b), middle vs bottom].