I wonder how can we make assumptions about the bird songs while not taking into account how birds perceive the sound. For humans it's easier, there were a plen

I wonder how can we make assumptions about the bird songs while not taking into account how birds perceive the sound. For humans it's easier, there were a plenty of studies done in that regards and there is even a separate science field for studying the human sound perception - Psychoacoustics. Humans perceive sound in bands (a band is a range of frequencies), not separate frequencies. And the size of bands vary per frequency so that in the voice range it's more narrow than, for example, high frequencies. The FFT fits very nicely into that picture and codecs were designed considering the human perception. As for animals, I don't know any studies in that regards. I would assume that the way of perception should be very similar to the one human has, at least on the mechanics level. As for the sensitivity and the size of bands as well as dynamic range - it's hard to say. I'd love to see some studies that dig into details there but it seems that it's very hard to do them. Animals don't give you a direct feedback.