Now that’s pretty specialized, and it’s unique; there’s just no other bird that does this. He’s moving his wings into postures that birds don’t normally move their wings into by flipping them upside down, he’s knocking them together at a rate that a mammal can’t even do, so that implies that there’s actually some special muscle physiology in these birds. We have an instrument. Where we once just had a functioning wing, we now have a musical instrument on the back of this bird, where we’ve got a feather that’s bent in just the precise way to allow it to lie on top of a precise set of ridges on the neighboring feather, and that feather itself is tuned to the frequency of sound. This explains why those two feathers, the sixth and the seventh, are so fat. It’s because they are like tuning forks. 1500 cycles a second is the frequency that they want to vibrate at. So this is a really complex, integrated, involved thing just to get the sound out of this animal. It turns out in the bird world that actually a lot of other birds do make sounds with their wings, and it also turns out that it’s more complex than we thought. However the Club-winged Manakin stands apart even among these really special birds in being the only bird that makes a tonal sound like a cricket by stridulating specialized feathers above its back.