Our chickens seem to eat almost anything small enough to get down their necks, especially if it's wriggling (baby mice and nestling birds are a favourite).
Only two things I've seen them not eat. One is orange peel, the other is slimy stinky maggots out of a really unpleasant, liquid carcase (a rat I think). Drier maggots seem to be acceptable, as does freshly chopped raw rat...
Oh, and bees. That's three things. ("No-one expects ...").