For example , bird feathers are used for lining and insulation , a typical example being that of the female common eider duck ( Somateria mollissima ) , which produces down feathers for lining its nest .
Not all self - secreted materials are developed specifically for that purpose .
Bird feathers are used for lining and insulation , a typical example being that of the female common eider duck ( Somateria mollissima ) , which produces down feathers for lining its nest .
Not all self - secreted materials are developed specifically for that purpose .