Most are either goose or duck feathers. Goose feathers are regarded as being superior to duck. This is because geese are larger than ducks, and the soft down clusters next to the skin are larger. This enables the goose down to trap more air than duck down, and so offer a higher level of insulation. A goose down mattress topper will be warmer than a duck down topper and both will be softer to lie on than a feather or foam topper.