Flapping Flight

There are two kinds of bird flight: flapping and gliding. During flapping flight, the bird beats its wings up and down. The large primary feathers in the wing do most of the propulsion; the smaller secondary feath­ers help to maintain lift. The wings move in two directions while flapping: up and down and in a circular or figure 8 move­ment. The wingtips move faster and farther than the rest of the wings. The smaller the bird, the faster its wings flap.

The downbeat is the power stroke. On the downbeat, the wing feathers overlap closely so that air cannot pass through them but is instead pushed downward. The wing moves downward and forward. The primary feathers are bent back at their tips so the wing performs like a
propeller, pulling the bird forward. Power is produced on the upbeat, too, although less so than on the downbeat. As the wing moves upward, the primary feathers are bent back and move apart a little, fanning open to allow air to slip through the gaps between them. This reduces wind resistance and saves energy.

THE SPEED OF BIRDS

Peregrine falcon: 200 miles per hour (320 kilometers per hour) in a dive.

Spinetailed swift: 105 miles per hour (170 kilometers per hour). Canvasback duck: 65 miles per hour (105 kilometers per hour).

Pigeon: 60 miles per hour (96 kilometers per hour).

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