Figure 5.

Only variation in the pitch of song syllables differs between juvenile subsong and adult song. A–D, Scatter plots of syllable duration by spectral feature (A, pitch; B, FM; C, entropy; D, pitch goodness) from a representative bird show that dispersion of syllable values for pitch is limited during subsong (black) when compared with adult song (gray)—all other features show similar variation during subsong and adult song. E, The developmental increase in variance (IQR) for the pitch of song syllables is significantly larger than that for FM, entropy, or pitch goodness (p < 0.0001).