Down jacket

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 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).

Human use

Down feathers were used by indigenous North Americans for religious ceremonies and as powerful symbols. In the stories of some cultures, the down feathers of an eagle were important gifts given by the bird to the story's hero.In the Ghost Dance, 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, which was sacred to the Ghost Dance, or of an eagle, which was sacred to all tribes.Zuniprayer sticks 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 rubbed eagle down feathers over rattlesnakes 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 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 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 g) of lower quality feathers per nest.In general, 50–60 nests will produce about one kilogram (2.2 pounds) of down feathers.This means that only a few thousand pounds of eider down is collected from wild nests each year.Approximately 70% of that harvest is from Iceland.

In Iceland and Scandinavia, colonies of more than 5,000 birds sometimes develop in "farmed" areas, while in some protected areas of the Novaya Zemlyaarchipelago, 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, gulls and other seabirds 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 In the United States, Federal Trade Commission 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 down, 10% goose feathers.

Down insulation is rated by fill power, 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, 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   in³/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 molds and dust mites. Pillows provide the most common source of exposure, though mattresses, comforters, outerwear and upholstery can also cause problems. A Finnish study has shown that true feather allergies are rare, with most issues caused by dust mites.

Types of down

• Duck down:

  • Eider down: This is considered to be the ultimate in duck down; it is collected from the female eider ducks' nests and has the largest duck down clusters. It is the worlds only down that is harvested in this manner as opposed to plucking the birds, dead or alive.

  
  

• Goose down:

  • Polish/Hungarian goose down: Widely considered to be the finest quality down clusters, they are larger than the norm and are mostly pure white in color.

  
  

• Feather-down combinations: Down compacts with age and is not appropriate for some applications; most down-filled pillow forms are stuffed with a combination of down and feathers. The presence of feathers adds weight, stability and bulk. Therefore, a mixture with more down will be lighter and fluffier than a pillow with a higher feather ratio.

• Marabou(t): Marabou (historically spelled with a T) is down from the marabou stork although turkey down is used as a substitute. It is widely used as a fashion trimming and in fly tying.