Figure 1. The Dark-billed Cuckoo is relatively common in disturbed Caatinga, also close to human habitations. This song was recorded in an area with Caatinga regrowth in various stages, between 3 and 20 years old, close to a water reservoir.

See fig. 2 for details of section "A" and fig. 3 for details of section "B".

Figure 2. Details of section "A" from fig. 1. To a human listener (at least to me), the initial part of the song sounds like a series of short narrow-band noise pulses, nearly like soft clicks. However, the spectrogram shows that the noise pulses are strongly amplitude-modulated, such that each pulse consists of a series of 3-4 shorter pulses.

DFT window size was reduced from the default 512 to 128 samples, to improve time resolution and thus visibility of the short pulses, which are less than 5 ms in duration.

Figure 3. Details of section "B" from fig. 1.