Salient points, INJ, I have no doubt. Ants too can do a very efficient demolition job on a carcass, but I doubt (in fact would reject) the idea that bird feathers are nutriment for scavengers. The reason for that attitude is that individual feathers, presumably resulting from natural 'moulting', are common and most certainly not a part of a drift of feathers produced by either direct attack or the efforts of scavengers. Who hasn't come across a particularly attractive feather from time to time and wondered what type of bird lost it?
[Dujon] Indeed, I'm sure that in your neck of the woods ants will be particularly efficient at cleaning up. I agree feathers are a bit different, but they must be destroyed fairly quickly if only because otherwise we'd be up to our necks in them. Also they are pretty much pure keratin which, despite its toughness, is none the less protein and so crying out to be recycled. I'm now into speculation, but I would suspect insects & bugs are likely to be the cleaning crew and will reprocess the feathers into chitin etc. Surely there's someone in the morniverse who can add a bit more scientific rigour at this point.