Fig 7. Examples of vocalization spectrograms from the following different bird species: (a) Aramides cajanea; (b) Rupornis magnirostris; (c) Piranga olivacea; (d) Piranga rubra; (e) Crypturellus cinereus; and (f) Crypturellus soui.

The two first examples illustrate that, although sounds of some species present an important content in low frequencies as in the case of speech (a), in general, their spectral characteristics are very distinct from the speech spectra (b); (c) and (d) show the acoustic similarity between sounds of different species, which may produce errors in the classification process; and (e) and (f) contain examples of very noisy spectrograms, which are very likely to be misclassified.