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Down feathers are the soft, fine feathers that lie underneath the tougher exterior feathers of some adult birds and help prevent the loss of body heat. Because of its light weight, compressibility, and ability to retain heat, down is considered the best insulation material for outdoor equipment and is used in goods such as jackets, pillows, and sleeping bags. The discovery of feathers encased in ancient amber suggests that what now-extinct creatures may have also sported down-like feathers? Discuss
Source: The Free Dictionary