Figure 6. Pressure control of F0 in sound production is redundant across avian taxa.

Spectrograms and oscillograms of spontaneous vocalisation (left) and representative pressure control spaces ex vivo (right) of (a) pigeon (Columba livia), (b) Barbary dove (Streptopelia risoria), (c) cockatiel and (d) Bengalese finch (Lonchura striata domestica). The F0 ranges of sounds produced ex vivo (grey vertical bar right of spectrogram) correspond well to the lower range of spontaneous vocalizations. Pressure control may allow higher F0 values, as indicated by the grey bar fading out. Iso-F0 contours (values in Hz) are overlaid on the pressure control spaces and shown in white when redundant for all three acoustics parameters (F0, SPL and WE), or black when not. In the Bengalese finch, the left hemisyrinx produces higher F0 than the right hemisyrinx, corroborating earlier in vivo studies70. (e) Spectrogram and oscillogram (left) of ostrich mating call, and ex vivo sound production including bronchial pressure (p_b) patterns underlying phonation (right). A complete pressure control space was not obtained for this species.