Book 31, Question 93
How do birds make music without their voices?
Not every bird sound comes from a syrinx.
A woodpecker drums on a hollow tree to make a loud rat-a-tat. A ruffed grouse beats its wings so fast that they make a deep, drum-like thump. The snipe dives through the air, and its stiff tail feathers whistle in the wind. Some hummingbirds make a sharp chirp by fluttering their tail feathers.