Feathers
Feathers
Feathers (/ˈfɛðərz/) are the unique external covering, or integument, of birds and some other species of animals. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty.
Etymology
The word feather derives from the Old English fether, which in turn is from the Proto-Germanic *feþrō.
Structure
Feathers are made primarily of keratin, a protein also found in hair, nails, and scales. They consist of a central shaft (rachis) with a series of vanes on either side. These vanes are composed of barbs, which branch into barbules. These structures interlock, giving the feather its shape and strength.
Types of Feathers
There are several types of feathers, each serving a different function. These include:
- Contour feathers, which shape the bird's body and provide coloration and flight capabilities.
- Down feathers, which provide insulation.
- Semiplume feathers, which provide insulation and fill out the bird's shape.
- Bristle feathers, which are sensory in function.
- Filoplume feathers, which monitor the position of the contour feathers.
Functions
Feathers serve many functions in birds, including flight, thermal insulation, waterproofing, and coloration for communication and camouflage. Some birds also use their feathers in courtship displays or as a means of making noise.
Evolution
The evolution of feathers is a subject of ongoing scientific study. It is generally agreed that feathers evolved from the scales of reptiles, although the exact pathway of this evolution is still a matter of debate.
Related Terms
- Plumage, the entire feather covering of a bird.
- Molt, the process by which birds shed old feathers and grow new ones.
- Preening, the act of grooming and maintaining feathers.
External links
- Medical encyclopedia article on Feathers
- Wikipedia's article - Feathers
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