Fig. 1.

Sound signals in different compartments of respiratory and vocal system in a ring dove (a) and Eurasian collared dove (b). Emitted, tracheal, and CTAS signals are from the same coo vocalization. The ICAS signal is from a different coo from the same individual. Shown are spectrograms (Upper) and power spectra (Lower; in averaged 20-Hz bins) of a 100-ms segment, centered on the time indicated with a dashed line in the spectrogram above. The intensity values in power spectra are relative to the intensity of f₀. The smaller peaks at integer multiples of 100 Hz in the CTAS signal of the ring dove (a) are an artifact attributable to electronic noise.