Many birds and some animals use a variety of man-made items in their nests. I've often seen red squirrel nests utilizing strips of plastic, plastic bags, and even dog hair. I've also seen grey squirrel nests made up of many man-made items. This red squirrel nest, made mostly of grass, bark strips and other fibres, was topped by a big pile of polyester filling from something! A coat, a cushion?