On several occasions I've found little fuzzy, brown grubs have eaten my feathers. I looked it up and it turns out to be the larval stage of a common carpet beetle. they will also eat sinew, rawhide, fur, and anything animal based. Take the bag of feathers and shake it to knock all the little grubs off the feathers, then put the feathers in a new bag in the freezer for a few days. Take the little grubs you find and put them in a huge bonfire and burn the little bastards till there's nothing but ash left. Those carpet beetles will destroy feathers, so kill them any chance you get. They seem to like dark, quiet places. Items that are handled regularly don't often get eaten, but the sinew that's in drawers or the feathers that are in closets are often infested. Of course you can use mothballs and that'll drive them out quick (or kill them if they can't get away from the fumes). Also, I had several bags of feathers, and one bag happened to fall on the floor...that one bag had the grubs in it and the feathers were all chewed up. The other bags were fine.
Seems the grubs live in the carpet, so don't keep anything like that on the floor, otherwise they'll find it and eat up your stash of feathers.
Hope that helps.
