Figure 2. Phrase length is defined by a typical time-scale and depends on context.

A, Probability density of phrase durations for all 6 birds (mode = .9416, .8132–1.407 95% bootstrap confidence interval, median = 1.3482, 1.3375–1.3589). B, A scatter plot of phrase duration plotted against syllable duration for 6 birds reveals no general correlation between phrase length and syllable length (r = .013,p = .90). C, Examples of the effect of phrase context on phrase duration. Each group of points (separated by dotted lines) indicates the duration of a different phrase type, while the colors (arbitrary) indicate different preceding phrase types. (These examples draw from all 6 birds, all phrase durations are given in Fig. S12).