Working with air

Wings are much bigger than arms. But being made mostly of feathers, they are also very light. Their shape uses the wind to make flying easier.

Getting a lift

From side on, you can see that a bird’s wing is flat underneath and curved on top. This means that the air passes faster above it than underneath it. The difference in air speed creates air pressure underneath the wing, which lifts it up. Aeroplane wings use exactly the same shape to help give them lift.

Flapping

Flapping helps a bird to push itself through the air. On the downstroke, the wing forces the air down – which pushes the bird up. At the same time, the wing tip tilts forward to push the air back. This pushes the bird forward. The upstroke raises the wings back into position for the next downstroke.

Flapping takes a lot of energy, and it is easier with smaller wings. Small birds, such as sparrows flap their wings in fast bursts. Larger birds, such as gulls, flap much more slowly and glide whenever they can.

Changing direction

A flying bird changes direction by altering the angle or shape of its wings. By tilting one wing down it can turn towards that side. See how this works by making a paper plane and tilting one wing down. To slow down or land, a bird fans out its tail and tilts its wings back to create more air resistance. Try tilting back the wings on your paper plane and see what happens.