Changes of dance performance within and among individuals.
Individual differences were calculated in (a) bobbing tempo and (b) the number of steps per bob (shaded bars: males, white bars: females). Bobbing tempo depended on (c) whether the partner was on the same perch and (d) whether birds were singing. Similarly, the number of steps depended on (e) whether the partner was on the same perch and (f) whether birds were singing. (a–f) All box plots show median, quartiles and minimum and maximum values. (c–f) Mean individual values (closed circles: males, open circles: females) and their within-individual changes are indicated.