Fig. 2.

Male and female syllables alternate precisely during duetting. The spectrogram (a, c) and amplitude waveform (b, d) of the combined male and female vocal traces are shown for exemplary duet bouts initiated by the male (a, b) or by the female (c, d) of Pair #4. Male signals are coded in blue and female signals are coded in red. Solid dark blue and dark red lines outline the root-mean-square envelope (see “Methods”) of the amplitude waveforms. Onset–onset intervals of male and of female duet syllables are given by values above the spectrograms