feathers


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feathers,

outgrowths of the skin, constituting the plumage of birds. Feathers grow only along certain definite tracts (pterylae), which vary in different groups of birds. Feathers develop from tiny projections of tissue (papillae) embedded in follicles and nourished by blood vessels in the dermis. When the feather is full grown, the blood supply is discontinued and the central shaft becomes hollow. A secretion of the thyroid gland stimulates the papilla to develop a new feather when one has been molted or pulled.

In a typical feather, barbs extend outward from the distal portion of the shaft, or rachis; smaller crosslinking barbules and hooks interlock neighboring barbs, forming a web that gives the feather both strength and flexibility. Down feathers, or plumulae, the first plumage of young birds and the protective undercoat of aquatic birds, lack these interlocking projections. Specialized feather forms are found in crests, top-knots, ruffs, and tail feathers. Bristles are modified feathers. The colors red, yellow, brown, and black are caused by pigment in the feathers. There are no blue pigments, and green and violet are rare; however, these colors, as well as iridescent effects, are caused by the reflection and diffraction of light.

Feathers are lightweight, durable, and in some cases waterproof. They have protective and decorative functions, but, aside from their role in bird flightflight,
sustained, self-powered motion through the air, as accomplished by an animal, aircraft, or rocket. Animal Flight

Adaptation for flight is highly developed in birds and insects. The bat is the only mammal that accomplishes true flight.
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, their most important capacity is heat retention. Feathers are believed to have evolved from reptilian scales in Mesozoic times, but little is definitely known about how they arose, and the feathers of ArchaeopteryxArchaeopteryx
[Gr.,=primitive wing], a 150 million-year-old fossil animal first discovered in 1860 in the late Jurassic limestone of Solnhofen, Bavaria, and described the following year.
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 and other early birds may have been too weak to be useful for flight. A number of feathered dinosaurs are known from the fossil record; one, Yutyrannus huali, was quite large (30 ft/9 m long) and had filamentlike feathers.

Feathers have been used by humans from ancient times for millinery and other ornamental purposes. The indiscriminate hunting of certain birds for their feathers has resulted in their near extinction; it is now prohibited by law in the United States.

Bibliography

See T. Hanson, Feathers (2011).

References in classic literature ?
Among the recruits who had enlisted he distributed feathers and ostrich plumes.
But suddenly the bunch of feathers stopped whirling, and then, to her amazement, the girl saw Billina crouching upon the prostrate form of a speckled rooster.
You've lost a lot of feathers, and one of your eyes is nearly pecked out, and your comb is bleeding
At that moment the man with the feathers ceased to gesticulate, and, with his hands placed upon his knees, was following, half-bent, the effort of six workmen to raise a block of hewn stone to the top of a piece of timber destined to support that stone, so that the cord of the crane might be passed under it.
Jemima Puddle-duck was rather surprised to find such a vast quantity of feathers.
She took care to do everything according to the old woman's bidding and every time she made the bed she shook it with all her might, so that the feathers flew about like so many snowflakes.
and when man wanted their flesh, their skins, or their feathers, there’s the place to seek them.
The party went to the theater, where they saw a play acted by foxes dressed in costumes of brilliantly colored feathers.
I am laughing because, in preening my feathers, I tickled myself under the wings.
She then laid twenty mattresses one upon another over the three peas, and put twenty feather beds over the mattresses.
As soon as the eagle saw itself free from its tormentors it plucked a feather from its wing, and, handing it to the Prince, said: 'Here, my kind benefactor, take this feather as a proof of my gratitude; should you ever be in need of my help blow this feather into the air, and I will help you as much as is in my power.
Janet loved me for it, just as she detested poor Esther because Esther had said so much shade was unhygienic and had objected to sleeping on a feather bed.