Down feathers
Encyclopedia
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s is a layer of fine feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
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 padding
Padding
Padding is thin cushioned material sometimes added to clothes. It is often done in an attempt to soften impacts on certain zones of the body or enhance appearance by 'improving' a physical feature, often a sexually significant one...
, used in goods such as jacket
Jacket
A jacket is a hip- or waist-length garment for the upper body. A jacket typically has sleeves, and fastens in the front. A jacket is generally lighter, tighter-fitting, and less insulating than a coat, which is outerwear...
s, bedding
Bedding
Bedding refers to the materials laid above the mattress of a bed for hygiene, warmth, to protect the mattress, and for decorative effect. Bedding is the removable and washable portion of a human sleeping environment. It is more easily and economically replaced than the bed itself...
, pillow
Pillow
A 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 bag
Sleeping bag
A 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 a bed is unavailable . 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
Old Norse
Old 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. The down feather is considered to be the "simplest" of all feather types. It has a short or vestigial rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...
(shaft), few barbs, and barbules that lack hooks. There are three types of down: natal down, body down and powder down. Natal down is the layer of down feathers that cover most birds at some point in their early development. Precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
nestlings are already covered with a layer of down when they hatch, while altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
nestlings develop their down layer within days or weeks of hatching. Megapode hatchlings are the sole exception; they are already covered with contour feathers
Pennaceous feather
Pennaceous feathers are also known as contour feathers. This type of feather is present in most modern birds, and has been shown in some species of maniraptoran dinosaurs....
when they hatch. Body down is a layer of small, fluffy feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s that lie underneath the outer contour feathers on a bird's body.
Powder down is a special type of down that occurs in a few groups of apparently unrelated birds. In some species, the tips of the barbules on powder down feathers disintegrate, forming fine particles of keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
, which appear as a powder, or "feather dust", 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 parrot
Parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...
s have powder down, with some species (including the Mealy Parrot
Mealy Parrot
The 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 tinamou
Tinamou
The 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 heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
s. The dust produced from powder down feathers is a known allergen
Allergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
in humans.
Function
The loose structure of down feathers traps air, which helps to insulate the bird against heat loss and contributes to the buoyancy of waterbirds. Species that experience annual temperature fluctuations typically have more down feathers following their autumn moult. There is some evidence that down feathers may also help to decrease the incidence of nestling cannibalism among some colonially nesting species, as the stiffness of the feathers make the young more difficult to swallow. Pollutants can reduce the efficiency of these functions. When oiled, for example, down feathers mat and clump together, which breaks down the bird's insulation and allows water to reach the skin.Female wildfowl use down feathers plucked from their own breasts to line their scrape nests. This process performs the dual function of helping to insulate the eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
and exposing the female's brood pouch—an area of bare skin, rich in blood vessels, which transmits heat very efficiently. Of the various items birds use to line their nests, down feathers provide the most effective insulation, though only when dry; wet down is the least effective insulator. Down may also help camouflage the eggs when the female is away from the nest, particularly as the birds often draw the feathers over their eggs before leaving.
Because a bird can eliminate heavy metals in its feathers and because feathers can be collected non-invasively and stored indefinitely, down feathers can be used to check for evidence of metal contamination in the bird's environment. Studies have shown a high level of correlation between the level of metal contamination in a bird's diet and the level found in its feathers, with the proportion of the chemicals found in its feathers remaining relatively constant (and relatively high for some metals).
Mutation
MutationMutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s that control the formation of down feathers have been recorded in a German White Leghorn flock. Although the elements of a normal down feather are present, a hyperkeratosis
Hyperkeratosis
Hyperkeratosis is thickening of the stratum corneum, often associated with a qualitative abnormality of the keratin, and also usually accompanied by an increase also in the granular layer...
of the feather's horny sheath after 16–17 days of incubation
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
results in the sheath not splitting as it should during the final stages of the feather's growth. Because of that abnormal splitting, the bird's down appears to be matted; chicks with this condition look bristly and singed and tend to be lighter in body weight than normal chicks are.
Human use
Down feathers were used by indigenousIndigenous peoples
Indigenous peoples are ethnic groups that are defined as indigenous according to one of the various definitions of the term, there is no universally accepted definition but most of which carry connotations of being the "original inhabitants" of a territory....
North Americans for religious ceremonies and as powerful symbols. In the stories of some cultures, the down feathers of an eagle
Eagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...
were important gifts given by the bird to the story's hero
Hero
A hero , in Greek mythology and folklore, was originally a demigod, their cult being one of the most distinctive features of ancient Greek religion...
. In the Ghost Dance
Ghost Dance
The Ghost Dance was a new religious movement which was incorporated into numerous Native American belief systems. The traditional ritual used in the Ghost Dance, the circle dance, has been used by many Native Americans since prehistoric times...
, a religious movement that became particularly widespread among the Plains Indians, each dancer held a painted feather that was tipped with a down feather painted with another color; the feathers were generally those of a crow
Crow
Crows form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-size jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several...
, which was sacred to the Ghost Dance, or of an eagle, which was sacred to all tribes. Zuni
Zuni mythology
Zuni mythology is the oral history, cosmology, and religion of the Zuni people. The Zuni are a Pueblo people located in New Mexico. Their religion is integrated into their daily lives and respects ancestors, nature, and animals. Due to a history of religious persecution by non-native peoples, they...
prayer stick
Prayer stick
A prayer stick is a stick-shaped object used for prayer.For example, the rituals of the Pueblo contain many prayers; thus the Zuñi have prayers for food, health, and rain. Prayer-sticks, that is sticks with feathers attached as supplicatory offerings to the "spirits", were largely used by the Pueblo...
s were also made using eagle down. While eagle feathers belonged to the Sun Priest, who planted them to the sun, other priests could use them if rain was needed, as the down is said to suggest "fleecy clouds that gather on the horizon before rain". The Hopi
Hopi
The Hopi are a federally recognized tribe of indigenous Native American people, who primarily live on the Hopi Reservation in northeastern Arizona. The Hopi area according to the 2000 census has a population of 6,946 people. Their Hopi language is one of the 30 of the Uto-Aztecan language...
rubbed eagle down feathers over rattlesnake
Rattlesnake
Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...
s being collected for their Snake Dances, in an effort to soothe and calm the reptiles.
For centuries, humans across the globe have used down feathers for insulation. Russian documents from the 1600s list "bird down" among the goods sold to Dutch merchants, and communities in northern Norway began protecting the nests of eider
Eider
Eiders are large seaducks in the genus Somateria. Steller's Eider, despite its name, is in a different genus.The three extant species all breed in the cooler latitudes of the Northern hemisphere....
ducks as early as 1890. Eiders are still "farmed" by people in Iceland, Scandinavia and Siberia. The birds are provided with nest sites and protected from predators, and down is collected intermittently during the nesting season without harming the nests or female ducks. The first collection is made roughly halfway through the incubation period, when some 0.75 oz (21.3 g) of high quality down is removed per nest. When the eggs have hatched and the young have left the area, the remaining down and breast feathers are gathered, typically resulting in another 0.75 oz (21.3 g) of lower quality feathers per nest. In general, 50–60 nests will produce about one kilo (2.2 pounds) of down feathers. This means that only a few thousand pounds of eider down is collected from wild nests each year.
In Iceland and Scandinavia, colonies of more than 5,000 birds sometimes develop in "farmed" areas, while in some protected areas of the Novaya Zemlya
Novaya Zemlya
Novaya Zemlya , also known in Dutch as Nova Zembla and in Norwegian as , is an archipelago in the Arctic Ocean in the north of Russia and the extreme northeast of Europe, the easternmost point of Europe lying at Cape Flissingsky on the northern island...
archipelago, nest densities exceed 13,000 per hectare (more than 5,260 per acre). On the other hand, the more nomadic indigenous peoples of Arctic Canada did not see down production as a reasonable source of income and tended to overexploit eider nests with "indifferent" collection of down feathers from the nests.
Although the down feathers of various species of wildfowl, gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s and other seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s have historically been used for insulation, most now come from domestic geese. Some 70 percent of the world's supply comes from China, typically from birds killed for their meat. Most of the rest comes from Europe and Canada, from birds harvested for meat or pâté
Pâté
Pâté is a mixture of ground meat and fat minced into a spreadable paste. Common additions include vegetables, herbs, spices, and either wine or cognac, armagnac or brandy...
.
A percentage of the world's supply of down feathers has been plucked from live birds, a practice which is condemned as cruel by animal welfare
Animal welfare
Animal welfare is the physical and psychological well-being of animals.The term animal welfare can also mean human concern for animal welfare or a position in a debate on animal ethics and animal rights...
groups. The precise percentage of down harvested in this manner is uncertain; while some references report that it is only a small fraction of the total (less than 1% in 2011), a 2009 Swedish documentary reported that it might be as much as 50–80% of the total supply. Although live-plucking is illegal in the United States and Europe, it is known to occur in two European countries (Poland and Hungary) and in China. Public sentiment against the practice has, in some countries, been strong enough that large retailers such as IKEA
IKEA
IKEA is a privately held, international home products company that designs and sells ready-to-assemble furniture such as beds and desks, appliances and home accessories. The company is the world's largest furniture retailer...
(a home furnishing chain) and Patagonia
Patagonia (clothing)
Patagonia, Inc. is a Ventura, California-based clothing company, focusing mainly on outdoor clothing. The company is a member of several environmental movements. It was founded by Yvon Chouinard in 1972....
(a clothing manufacturer) have been forced to alter product lines to eliminate the use (or possible use) of live-plucked down.
In the United States, Federal Trade Commission
Federal Trade Commission
The Federal Trade Commission is an independent agency of the United States government, established in 1914 by the Federal Trade Commission Act...
regulations require that any product labeled "100% Down" must contain only down feathers, while products labeled simply "Down" can contain a mixture of fiber and feathers. In addition, products labeled as "Goose Down" must contain at least 90% goose feathers. Down insulation is rated by fill power
Fill power
Fill 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...
, which is the number of cubic inches displaced by a given ounce of down (in3/oz). To measure fill power, an ounce of down is placed into a graduated cylinder
Graduated cylinder
A graduated cylinder, measuring cylinder or graduate is a piece of laboratory equipment used to accurately measure the volume of a liquid. Water displacement can be used to find out the volume of a solid. Graduated cylinders are generally more accurate and precise for this purpose than flasks and...
, and a small weight is dropped in on top of it; the volume below the weight indicates the fill power. Eider down has the highest fill power, at 1200. However, even down with a fill power as low as 550 still provides reasonably good insulation. 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 n3/oz (230–520 cm3/g). Down rated 500-650 in3/oz (290–375 cm3/g) is warm enough and light enough for most conditions, and 800-900 in3/oz (460–520 cm3/g) fill is used for very lightweight and/or very cold-weather gear.
Down is warm, lightweight and packable. If well cared for, it retains its loft up to three times longer than do most synthetics. However, when it is wet, the thermal properties of down are virtually eliminated. Down forms clumps if exposed to dampness or moisture, and will mildew if left damp. In addition, it will absorb and retain odors.
Down feathers tend to become more allergenic as they age, as they become contaminated with mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
s and dust mites. Pillows provide the most common source of exposure, though mattresses, comforter
Comforter
A comforter is a type of blanket. Comforters are intended to keep the user warm, especially during sleep, although they can also be used as mattress pads. Comforters are generally large and rectangular in shape, filled with natural or synthetic insulative material and encased in a shell/covering....
s, outerwear
Outerwear
-List of outerwear:* Jacket* Coat* Mittens* Cloaks* Hats* Poncho* Rain pants* Trousers* Scarves*Gloves...
and upholstery
Upholstery
Upholstery is the work of providing furniture, especially seats, with padding, springs, webbing, and fabric or leather covers. The word upholstery comes from the Middle English word upholder, which referred to a tradesman who held up his goods. The term is equally applicable to domestic,...
can also cause problems. A Finnish study has shown that true feather allergies are rare, with most issues caused by dust mites.
Dinosaurs
Feathers found in amber in western France and Canada suggest that some dinosaurDinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s may have had primitive, down-like feathers.