The hummingbird is constantly on the move and lives mainly in the air to browse its territory, search for food, or attract the attention of females. Even to change places on a branch, it tends to fly briefly rather than walk. Its flight speed is spectacular. Wind tunnel studies cited by American Scott Weidensaul have measured flights of up to 43 mph (70 km/h) for some tropical species, and it is commonly believed that it can reach 62 mph (100 km/h) in the wild with the help of favorable winds. Capable of flapping its wings up to 200 times per second, the hummingbird can hover or perform impressive dives. A simple modification of the incidence of its wings, that is to say their angle of attack in the air, also allows it to fly backwards, an ability only hummingbirds possess.