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Fig. 6 | BMC Zoology

Fig. 6

From: The hummingbird syrinx morphome: a detailed three-dimensional description of the black jacobin’s vocal organ

Fig. 6

Black jacobin vocalizes in a wide frequency range with rapidly modulated vibratos. In a, spectrogram (frequency) and oscillogram (relative amplitude) of the three vocalization types produced by the black jacobin in the wild: low-pitched, chirps and high-pitched. The dots represent the average fundamental frequency for the respective vocalization on their left, and the whisker, the standard deviation. In b, an example of crest-trough detection in the high-pitched fragment (indicated by the red arrow) obtained by our customized R function. Red circles indicate the crest, and blue the trough; the difference between them is the vibrato extent. Note that the overlap of fundamental frequency contour and spectrogram are computed with different functions which induce a slight mismatch in the graphic representation. In c, the vibrato rate is calculated as the number of crest and trough pairs per second given in Hz, and the mean extent for each syllable/segment is calculated in kHz. The cross indicates means and arrows the standard deviation. Circles represent the data points obtained by an example of vibrato produced by a human singer (n = 12 vibrato segments in one song), triangles for Eurasian skylark (Alauda arvensis) (n = 11 syllables from two birds) and squares represent data points for the black jacobin (n = 18 syllables from three birds). See the Methods for the source of the sound recordings

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