Among the functional kind are what are known as down feathers. These fluffy, soft, formless feathers provide insulation for the bird keeping it warm in winter and cool in summer. Some birds, like the elder duck, use excess down feathers to insulate the nest of its babies. Contour feathers are designed to streamline the bird for flight. Their centrally located shaft is slightly curved to fit body surfaces always pointing backward from the beak and towards the tail.
Flight feathers provide lift and movement for the bird through the air.
These feathers, arranged in particular order at the extremity of each wing, are the propellers that provide lift and movement for the bird. They are able to turn on their axis, enabling them to overlap tightly on the downbeat yet to open on the upbeat. Other flight feathers in the bird s tail are controlled by strong tail muscles. Thus the feathers can be tilted, depressed, fanned out or folded to act as the perfect rudder. Apart from these feather types, many birds have feathers that are particular to their needs.