The big, stiff feathers on a bird's wings and tail are called flight feathers. These give it the push it needs for flying. A bird adjusts them to change direction or speed - just like the flaps on an aircraft's wings and tail.
Flightless birds have no proper flight feathers: all their feathers are limp and floppy.
The smaller feathers that cover a bird’s body are called contour feathers. They lie flat against its body to protect it from wind, cold and sun. They also give its body a smooth, streamlined shape for flying.
Birds are warm-blooded, and have to keep a body temperature of about 40°C. Under their contour feathers are tiny soft feathers called down, which lie against the skin and keep the bird warm. Down is great at keeping in warmth – which is why people use it to make quilts and duvets. In cold weather, a bird also fluffs out its contour feathers to trap a layer of warm air.
How feathers look can be just as important as what they do. Some birds use their feather patterns for camouflage – such as a nightjar, whose feathers look just like dead leaves. Others use them to impress a mate, such as a peacock, with its dazzling display feathers on its rump.
All these feathers don’t just grow anywhere on a bird. They are arranged in lines and patterns, each with a different name. The long flight feathers are called primaries, the shorter flight feathers are called secondaries, and the small feathers that cover their bases are called coverts. Learning the names of these different feather areas helps you to describe the birds you see.
View this page online at http://www.rspb.org.uk/youth/learn/adaptation/flight/featherswork.asp