Figure 2
Sample spectrograms and acoustic measures for estrildid song syllables. (a) ZF song syllables are predominantly ‘broadband’ with multiple harmonic bands and “noisiness” between those, (b) while LF songs contain characteristically “clean” and tonal syllables. Violin plots show the distributions of 4 acoustic features that were measured from each species song for comparison. Features shown here were selected to provide contrasts for the degrees to which species may be similar or different based on the specific acoustic features considered. Horizontal line across each violin shows the distribution’s median value. (c) Mean frequency distinguished the songs of Australian (M ± SD = 3050 ± 661 Hz), Southeast Asian (M ± SD = 3847 ± 882 Hz), and African (M ± SD = 5031 ± 872 Hz) species. (d) Spectral flatness differed between African songs and those of other species except LFs. (e) Syllable duration measures overlapped among species, but the distributions of syllable duration for each species differed. (f) Dominant frequency slope, a spectrotemporal feature, differed little by species. The number of syllables outside of the plotted range is specified for each species.
