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Feather

2007 Schools Wikipedia Selection. Related subjects: Birds

   parts of a contour feather
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   parts of a contour feather

   Feathers are one of the epidermal growths that form the distinctive
   outer covering, or plumage, on birds. They are the outstanding
   characteristic that distinguishes the Class Aves from all other living
   groups. Other Theropoda also had feathers (see Feathered dinosaurs).

Characteristics

   Extreme closeup of the feathers of a baby Yellow-headed Parrot.
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   Extreme closeup of the feathers of a baby Yellow-headed Parrot.
   A white feather
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   A white feather

   Feathers are among the most complex structural organs found in
   vertebrates: integumentary appendages, formed by controlled
   proliferation of cells in the epidermis, or outer skin layer, that
   produce keratin proteins. The β-keratins in feathers, beaks and claws —
   and the claws, scales and shells of reptiles — are composed of protein
   strands hydrogen-bonded into β-pleated sheats, which are then further
   twisted and crosslinked by disulfide bridges into structures even
   tougher than the α-keratins of mammalian hair, horns and hoof.

   Feathers insulate birds from water and cold temperatures. Individual
   feathers in the wings and tail play important roles in controlling
   flight. These have their own identity and are not just randomly
   distributed. Some species have a crest of feathers on their heads.
   Although feathers are light, a bird's plumage weighs two or three times
   more than its skeleton, since many bones are hollow and contain air
   sacs. Colour patterns serve as camouflage against predators for birds
   in their habitats, and by predators looking for a meal. As with fish,
   the top and bottom colors may be different to provide camouflage during
   flight. Striking differences in feather patterns and colours are part
   of the sexual dimorphism of many bird species and are particularly
   important in selection of mating pairs. The remarkable colors and
   feather sizes of some species have never been fully explained.

   There are two basic types of feather: vaned feathers which cover the
   exterior of the body, and down feathers which are underneath the vaned
   feathers. The pennaceous feathers are vaned feathers. Also called
   contour feathers, pennaceous feathers are distributed over the whole
   body. Some of them are modified into remiges, the flight feathers of
   the wing, and rectrices, the flight feathers of the tail. A typical
   vaned feather features a main shaft, called the rachis. Fused to the
   rachis are a series of branches, or barbs; the barbs themselves are
   also branched and form the barbules. These barbules have minute hooks
   called barbicels for cross-attachment. Down feathers are fluffy because
   they lack barbicels, so the barbules float free of each other, allowing
   the down to trap much air and provide excellent thermal insulation. At
   the base of the feather, the rachis expands to form the hollow tubular
   calamus, or quill, which inserts into a follicle in the skin.

   The Dyck texture is what causes the colours blue and green in most
   parrots. This is due to a texture effect in microscopic portions of the
   feather itself, rather than pigment, or the Tyndall effect as was
   previously believed.

   The spectacular red feathers of certain parrots owe their vibrancy to a
   rare set of pigments found nowhere else in nature.
   Two feathers
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   Two feathers

   A bird's feathers are replaced periodically during its life through
   molting, new feathers are formed through the same follicle from which
   the old ones were fledged.

   Some birds have a supply of powder-down feathers which grow
   continuously, with small particles regularly breaking off from the ends
   of the barbules. These particles produce a powder that sifts through
   the feathers on the bird's body and acts as a waterproofing agent and a
   feather conditioner. Most waterbirds produce a large amount of powder
   down. Waterproofing can be lost by exposure to emulsifying agents due
   to human pollution. Feathers can become waterlogged and birds may sink.
   It is also very difficult to clean and rescue birds whose feathers have
   been fouled by oil spills.

   Bristles are stiff, tapering feathers with a large rachis but few
   barbs. Rictal bristles are bristles found around the eyes and bill.
   They serve a similar purpose to eyelashes and vibrissae in mammals.

Evolution

   Feathers most likely originated as a filamentous insulation structure,
   or possibly as markers for mating, with flight emerging only as a
   secondary purpose. It has been thought that feathers evolved from the
   scales of reptiles, but recent research suggests that while there is a
   definite relationship between these structures, it remains uncertain
   the exact process. (see Quarterly Review of Biology 77:3 (September
   2002): 261-95). Experiments show that the same protein (when missing
   before birth) that causes bird feet to stay webbed, causes bird scutes
   and scales to become feathers.

Feathered dinosaurs

   Although birds use feathers primarily for flight, several dinosaurs
   have been discovered with feathers on their limbs that would not have
   functioned for flight. One theory is that feathers originally developed
   on dinosaurs as a means of insulation; those small dinosaurs that then
   grew longer feathers may have found them helpful in gliding, which
   would have begun the evolutionary process that resulted in some
   proto-birds like Archaeopteryx and Microraptor zhaoianus. Other
   dinosaurs discovered with feathers include Pedopenna daohugouensis,
   Sinosauropteryx, and Dilong paradoxus. Currently the question is
   whether birds are deinonychosaurians or dromaeosaurids, not whether
   birds are dinosaurs. It has been suggested that Pedopenna is older than
   Archaeopteryx, however, their age remains doubted by some experts.
   Dilong is a tyrannosauroid which predates Tyrannosaurus rex by 60 to 70
   million years.

Human uses

   Shaft of Indian Peacock tail feather
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   Shaft of Indian Peacock tail feather

   Feathers have a number of utilitarian and cultural and religious uses.

   Utilitarian Functions

   Feathers are both soft and excellent at trapping heat; thus, they are
   sometimes used in high-class bedding, especially pillows, blankets, and
   mattresses. They are also used as filling for winter clothing, such as
   quilted coats and sleeping bags; goose down especially has great loft,
   the ability to expand from a compressed, stored state to trap large
   amounts of compartmentalized, insulating air. Bird feathers have long
   been used for fletching arrows and in the past were used for ink pens.
   They have also been put to use as sexual aids; see feather-dancing.
   Another human use is tickling for their soft feeling. Colorful feathers
   such as those belonging to pheasants have been used in the past to
   decorate hats and fishing lures. During the late 19th and early 20th
   Centuries a booming international trade in plumes, to satisfy market
   demand in North America and Europe for extravagant head-dresses as
   adornment for fashionable women, caused so much destruction (for
   example, to egret breeding colonies) that a major campaign against it
   by conservationists caused the fashion to change and the market to
   collapse.

   Cultural and Religious Uses

   Eagle feathers have great cultural and spiritual value to American
   Indians as religious objects. The religious use of eagle and hawk
   feathers are governed by the eagle feather law (50 CFR 22), a federal
   law limiting the possession of eagle feathers to certified and enrolled
   members of federally recognized Native American tribes.

   Various birds and their plumages serve as cultural icons throughout the
   world, from the hawk in ancient Egypt to the bald eagle and the turkey
   in the United States. In Greek mythology, Icarus tried to escape his
   prison by attaching feathered wings to his shoulders with wax, which
   melted near the Sun.

   Retrieved from " http://en.wikipedia.org/wiki/Feather"
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   with only minor checks and changes (see www.wikipedia.org for details
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