UC Davis School of Veterinary Medicine

 

Feathers

Feathers evolved from the scales of reptiles.

Feathers are made out of keratin, the same protein found in hair and nails.

Feathers do not appear randomly on the body, they grouped by feather tracts called pterylae. On most birds the tracts run down the back of the head along the spine, from the throat down both sides of the chest and stomach, along the leading edge of the wings, and behind the legs.

There are several types of feathers, each with its own purpose.

Contour feathers are surface feathers of the body, wings, and tail.

Rectrices are the long contour feathers of the tail.

The tail feathers act as brakes and a rudder, controlling the orientation of the flight. There are 12 tail feathers.
The bases of the flight feathers are covered with smaller contour feathers called coverts. There are several layers of coverts on the wing. Coverts also cover the ear.

 

Remiges are the flight feathers of the wing. Primaries extend from the "hand," secondaries from the "arm," and tertiaries located closest to the body.

The primaries attach to the metacarpal (wrist) and phalanges (finger) bones at the far end of the wing and are responsible for forward thrust.

 

 

 

The secondaries attach to the ulna, a bone in the middle of the wing, and are necessary to supply 'lift.' They are also used in courtship displays.

 

 

 

Down feathers are small, soft, fluffy, and are found under the contour feathers. Down feathers trap air in an insulating layer next to the skin, protecting the bird from heat and cold.

 

 

Semiplume provide form, aerodynamics, and insulation. They also play a role in courtship displays. They have a large rachis (the part above the calamus which barbs extend), but loose (plumaceous) vanes. They may occur along with contour feathers or in separate pterylae.

 

 

Filoplumes are very fine, hair-like feathers, with a long shaft, and only a few barbs at their tips. They are located along all the pterylae. They are thought to have a sensory function, possibly adjusting the position of the flight feathers in response to air pressure.

 

 

Bristle feathers are usually found around the eyelids, nares (nostrils), and mouth). They are thought to have both a sensory and protective function.