Figure 3.
Sequence-dependent differences in phonology. a, Spectrogram of ∼1 s of song from BF04. The convergent syllable B is highlighted: AB in green and KB in red. b, Average spectrograms of 10 examples of syllable B in each sequence. c, Histogram of the durations of syllable B in each sequence. d, Mean ± 1 SD ellipses for the first two principal components (PC1 and PC2) of syllable B found in each sequence, as well as all other syllables from the bird's repertoire (in gray) for comparison. Syllable AB is significantly different from KB at p < 0.0001. e, Spectrogram of ∼1.5 s of song from BF05. Note that the letters assigned to each syllable are arbitrarily chosen for each bird, so that the acoustic similarity of syllable B in this case (for bird BF05) to syllable B from bird BF04 is not meaningful. The divergence from syllable B is highlighted: BC in green and BK in red. f, Average spectrograms of 10 examples of syllable B in each sequence. g, Histogram of the pitch of syllable B in each sequence. h, Mean ± 1 SD ellipses for the first two principal components of syllable B found in each sequence, as well as all other syllables from the bird's repertoire (in gray) for comparison. Syllable BB is significantly different from BC at p < 0.0001.