Out my window, I can hear one of the resident hummingbirds performing his mating dives. The dives produce a birdcall which is actually produced by the bird’s feathers as he comes out of a high-speed dive.

This particular fellow is acoustically interesting because he seems to have the ability to change the pitch and timbre of the call, sometimes higher, sometimes lower. I suppose it could be that he’s attracting conversation from a member of a different species.