Feathers are a unique adaptation of birds. Feathers are made up of keratin, an insoluble protein that is also found in mammalian hair and reptilian scales. In general, feathers consist of the following structures:
- calamus - the hollow shaft of the feather that attaches it to the bird's skin
- rachis - the central shaft of the feather to which the vanes are attached
- vane - the flattened part of the feather that is attached on either side of the rachis (each feather has two vanes)
- barbs - the numerous branches off the rachis that form the vanes
- barbules - tiny extensions from barbs that are held together by barbicels
- barbicels - tiny hooks that interlock to hold the barbules together
Birds have several different types of feathers and each type is specialized to serve a different function. In general, feather types include:
- primary - long feathers located at the tip of the wing
- secondary - shorter feathers located along the trailing edge of the inner wing
- tail - feathers attached to the bird's pygostyle
- contour (body) - feathers that line the bird's body and provide streamlining, insulation, and waterproofing
- down - fluffy feathers located under the contour feathers that serve as insulation
- semiplume - feathers located under the contour feathers that serve as insulation (slightly larger than down feathers)
- bristle - long, stiff feathers around the bird's mouth or eyes (the function of brislte feathers is not known) (Sibley 2001, 17-18)
Feathers suffer wear and tear as they are exposed to the elements. Over time, the quality of each feather deteriorates and thus comprimises its ability to serve the bird in flight or to provide insulation qualities. So to prevent feather deterioration, birds shed and replace their feathers periodically in a process called molting.
Sources
- Attenborough, David. 1998. The Life of Birds. London: BBC Books.
- Sibley, David Allen. 2001. The Sibley Guide to Bird Life & Behavior. New York: Alfred A. Knopf.
- The University of California, Berkely (UCB). 2006 (Accessed Online). Museum of Paleontology.
