Hummingbirds are birds in the family Trochilidae, and are native to the Americas. They can hover in mid-air by rapidly flapping their wings 12–90 times per second (depending on the species). They can fly backwards, and are the only group of birds able to do so. Their English name derives from the characteristic hum made by their rapid wing beats. They can fly at speeds exceeding 15 m/s (54 km/h; 34 mph).