Many of the world’s smallest hummingbirds, including the West Coast’s Anna’s and the East Coast’s ruby-throated, execute display dives to seduce females and drive away intruders. A characteristic chirp at the bottom of the Anna’s dive, thought by many to be vocal, has now been shown to result from a split-second flaring of the tail feathers. Tests prove that tail feather vanes act like a reed in a clarinet to produce the beep.