Birds fly far better than any machinery mankind has yet made and like our machines they use their wings and tails in a variety of ways to achieve their expertise. Bird flight is dependent on the shape of the birds wings and the way they use them. Generally, bird flight can be divided into two modes of functioning, i.e. gliding or soaring flight, and flapping or powered flight. The dynamics of bird flight like all physical actions are governed by the laws of physics. In its simplest expression, flying is a balance between two sets of forces.
Lift is generated by the flow of air over the wings.
The red line is the leading edge, the air first hits the wing here. It travels up over the green line and then down the back of the wing where it leaves the wing at the blue line, the trailing edge. Basically, birds wings are not flat but are shaped like an aerofoil - concave. Air passes over or under the wing as the bird moves forward, or as the wind blows. The air that moves over the top of the wing has further to travel to get across the wing, thus it speeds up.