Contour Feathers
The wing, tail, and body feathers are the most important feathers; all are contour feathers and provide for flight, aerodynamics, and weatherproofing. (Countour and other feather types are discussed on Five Types of Feathers.
Above is the right wing of a White-tailed Eagle (Haliaeetus albicilla). The primary feathers on the outer wing provide propulsion through the air while the secondary and less so the tertiary feathers provide lift. The covert feathers streamline the wing for aerodynamics. The tail feathers or remiges of the Dark-eyed Junco (below) provide lift and steering, the base of the remiges is covered by upper tail coverts.
The tail feathers or remiges of the Dark-eyed Junco (Junco hyemalis) (left) provide lift and steering, the base of the remiges is covered by upper tail coverts.
The white outer tail feathers, usually only seen in flight, probably serve to keep a flock together. Another explanation is that if a predator keys in on the white outer tail feathers while the junco is in flight and the white feathers disappear, as they do, when the junco lands, the predator misses the mark.
Birds are covered all over with the exception of beak, feet, and legs with contour feathers for aerodynamics and protection against the elements, such as the Eastern Yellow Robin (Eopsaltria australis) (right) of Australia exhibits.
There are some birds that have feathers covering their feet such as the Rock Ptarmigan (Lagopus muta) (below) but these are down or semiplumes, not contour, feathers.
