Below: picture shows the flapping motion of a common bird.
ability to fly is surely the most remarkable feature of birds. Other creatures
such as insects and bats can fly, but it is birds that have made the sky
their own. Nevertheless, for all the work that has been done on aerodynamics,
we still know remarkably little about some aspects of bird flight. Aircraft
engineers have tended to study the fixed wings of aeroplanes. But the bird's
wing is flexible; birds can alter not only the size of the wing, but also
its shape. An aeroplane flies because its wings generate enough lift by
the plane's forward movement threw the air to overcome its weight.