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{{For|the record label|Duck Down Records}}
The
down of
birdBirds are winged, bipedal, endothermic , vertebrate animals that lay eggs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the ...
s is a layer of fine
featherFeathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are considered the most complex integumentary structures found in vertebrates. They are among the outstanding characteristics that distinguish the extant Aves from other living groups....
s found under the tougher exterior feathers. Very young birds are clad only in down.
Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and
paddingIn fashion, padding is material sometimes added to clothes. It is often done in an attempt to enhance appearance by 'improving' a physical feature, often a sexually significant one...
, used in goods such as
jacketA jacket is a type of sleeved hip- or waist-length garment for the upper body. For clothing older than the mid-nineteenth century, a distinction is often maintained with a coat, but in many instances the terms are now interchangeable. A jacket is generally shorter, ending just below the waist, and...
s,
beddingBedding refers to the materials laid above the mattress of a bed for warmth and decorative effect. Bedding does not include the mattress, box spring and bed frame. Down materials are often used for warmth in bedding.-Bedding sizes:...
,
pillowA pillow is a large cushion support for the head, usually used while sleeping in a bed, or for the body as used on a couch or chair. There are also throw pillows , which are pillows that are purely decorative and not designed for support or comfort...
s and
sleeping bagA sleeping bag is a protective "bag" for a person to sleep in, essentially a blanket that can be closed with a zipper or similar means, and functions as a bed in situations where it is impractical to carry around a full bed . Its primary purpose is to provide warmth and thermal insulation...
s. The discovery of feathers trapped in ancient amber suggests that some species of dinosaur may have possessed down-like feathers.
Description and etymology
The word
down comes from the
Old NorseOld Norse is a North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age, until about 1300....
word
dūnn, which had the same meaning as its modern equivalent.
Body down
Body down is a layer of small, fluffy
featherFeathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are considered the most complex integumentary structures found in vertebrates. They are among the outstanding characteristics that distinguish the extant Aves from other living groups....
s that lie underneath the outer
contour featherPennaceous feathers are also known as contour feathers and are present in most modern birds and in some species of maniraptoran dinosaurs.Pennaceous feathers have a central shaft with vanes branching off to either side...
s on a bird's body. Down feathers have a short or vestigial
rachisThe rachis is the main axis of the inflorescence, or spike, of wheat and other cereals, to which the spikelets are attached. It is also the part of the axis that the pinnae are attached to in ferns, the main stem of a compound leaf , or the main axis in compound inflorescences in other...
, few
barbBarbs are a series of branches fused to the rachis of a feather. The barbs themselves also have branches called barbules, which have hooks that lock the barbs together.-References:*...
s, and
barbuleBarbules are a part of the tree formed by feathers : the trunk, or axis, being the rachis and the barbs the main boughs, barbules are the secondary branches.Barbules have minute hooks called barbicels for cross-attachment.-References:*...
s which lack hooks.
Natal down
Most species of birds are covered with down feathers at some point in their early development. The exception are the Megapodes, which are already covered with contour feathers when they hatch.
Powder down
Powder down is a special type of down. It occurs in a few groups of apparently unrelated birds and thus is probably an example of
convergent evolutionConvergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, birds and bats do, and are capable of powered flight. The wings are similar in...
.{{Citation needed|date=June 2009}} In some species, the tips of the barbules on powder down feathers disintegrate, forming fine particles of
keratinKeratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but un-mineralized structures found in reptiles, birds, amphibians, and mammals...
, which appear as a powder among the feathers. These feathers grow continuously and are not molted. In other species, powder grains come from cells that surround the barbules of growing feathers. These specialized feathers are typically scattered among ordinary down feathers, though in some species, they occur in clusters.
All
parrotParrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most warm and tropical regions. The order is subdivded in three families: the Psittacidae , the Cacatuidae and the Nestoridae...
s have powder down, with some species (including the
Mealy ParrotThe Mealy Amazon or Mealy Parrot is among the largest parrots in the Amazona genus, the Amazon parrots. It is a mainly green parrot with a total length of 38-41 cm . It is endemic to tropical Central and South America.-Range, common names and races:The Mealy Amazon occurs in tropical Central...
) producing copious amounts. It is also found in
tinamouThe tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....
s and
heronThe herons are wading birds in the Ardeidae family. There are 64 recognised species in this family. Some are called egrets or bitterns instead of herons....
s.
Birds with powder down usually have a reduced
uropygial glandThe uropygial gland, or, more informally, the preen gland is a gland found in the large majority of birds that secretes an oil that birds use for preening. The chief compounds of preen oil are diester waxes called uropygiols....
, but not all birds with vestigial or missing uropygial glands possess powder down.
Function
The loose structure of down feathers traps air, which helps to insulate the bird against heat loss.
Human use
Down offers excellent thermal properties, and has good lofting characteristics. This means that the down traps small pockets of air efficiently. The small pockets of air provide the thermal barrier. Down has the added property that it can be packed into a very small space.
For outdoor equipment, down is considered to be the single best insulating material available due to its light weight, compressibility, and heat retention. Down insulation can be quite expensive, so alternatives, known as synthetic insulation, are available. Synthetic insulation types generally cost less and are usually not as lightweight or as compressible as down. However, synthetic insulations work better when wet and are easier to dry, whereas down insulation does not work at all when wet and takes a very long time to dry out. Thus people who expect a significant amount of rain when camping will either bring a down sleeping bag with a water-resistant shell, or a bag with synthetic fill.
Down insulation is rated by
fill powerFill power is a measure of the loft or "fluffiness" of a down product that is loosely related to the insulating value of the down. The higher the fill power the more insulating air pockets the down has and the better insulating ability. Fill power ranges from about 175 cm³/g for feathers to around...
, measured as the number of cubic inches displaced by a given ounce of down (in
3/oz). Higher fill-power downs will thus insulate better than lower fill-power downs of the same weight. Insulation in most outdoor equipment ranges from about 400 to 900 in
3/oz (230-520 cm
3/g). Down rated 500-600 in
3/oz (290-360 cm
3/g) is warm enough and light enough for most conditions, and 800-900 in
3/oz (460-520 cm
3/g) fill is used for very lightweight and/or very cold-weather gear.
When wet the thermal properties of the down are virtually eliminated, making it a worse insulator than most equally wet synthetic fills. Compressed down is also a very poor insulator, and thus sleeping bags insulated with down require the use of a
sleeping padIn camping, a ground pad, sleeping pad, sleeping mat or roll mat is a simple device often used in conjunction with a sleeping bag. Its purpose is to provide padding and thermal insulation...
to provide insulation from warmth that would otherwise be conducted into the ground.
Methods of harvesting
Down can be collected in a variety of ways. Birds which provide the feathers may be used for other purposes, for example to provide
meatMeat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat, but it may also describe other edible tissues such as organs, livers, skin, brains, bone marrow, kidneys, or lungs...
. Some birds are killed solely for their down, while some birds (particularly some geese) are periodically live-plucked of their breast
featherFeathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are considered the most complex integumentary structures found in vertebrates. They are among the outstanding characteristics that distinguish the extant Aves from other living groups....
s. Some birds, such as the eider duck, line their nests with down, and such down is harvested safely after the young leave the nest.
Animal welfareAnimal welfare, the health and well-being of animals, represents a systematic concern for people who believe that nonhuman animals are sentient beings that deserve consideration, respect, and care...
groups consider the live-plucking of down to be a painful procedure and cruel, particularly since birds must undergo down collection repeatedly.{{Citation needed|date=March 2009}}
Dinosaurs
Feathers found in amber in western France suggests that some
dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
s may have had primitive, down-like feathers.