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. Down is a fine
thermal insulator and
padding, used in goods such as
jackets,
bedding (
duvets),
pillows and
sleeping bags. The discovery of feathers trapped in ancient amber suggests that some species of dinosaur may have possessed down-like feathers.