Down feather
 

Down is a fine thermal insulator and padding, used in goods such as jackets, bedding, pillows and sleeping bags. The discovery of feathers trapped in ancient amber suggests that some species of dinosaur may have possessed down-like feathers. The word down comes from the Old Norse 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 (shaft), few barbs, and barbules that lack hooks. The down of birds is a layer of fine feathers 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.
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.
Down feathers were used by indigenous North Americans for religious ceremonies and as powerful symbols. 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 In the stories of some cultures, the down feathers of an eagle were important gifts given by the bird to the story's hero; 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.