this is what i heard..take a pair of panty hose, drop the bird in a leg head first, this way all of the feathers are protected, when it is time to get him out, just cut the hose where the head is and slide it down over the feathers....
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Don't go leaving your ethics in the truck
Aside from the panty-hose (jokes aside), you should try to ensure bird doesn't flop around to much (losing feathers in the process), and with damp paper towels, carefully wipe away any blood on the feathers. Also I think most taxidermists want the bird whole, don't gut it or anything.