i have a Muscovy drake, he's a year and a half. he's totally white but his wing feathers are getting brown and brittle, the barb is falling off and all thats left on most of them is the Rachis. i feed him about 3/4 of a cup of oats each day, but he roams around our (very small) yard so he'll eat bugs and grass and things like that. im wondering if there is some way i can fix his feathers, my dad thinks its unhealthy or something is wrong with him. i know its probably normal but my dad is concerned and plus its not very pretty. could it be his diet? does he need vitamins? thanks in advance!