That info on parasites is pretty scary! Not sure what to make of it!
Never heard of The Book of Ducks. Is it a regular go to, Lydia? Mine certainly are not in horrendous conditions. With frozen snow and hose issues their outside areas are not as good as normal (which is very good) but still just somewhat soiled with their own. The three do choose to spend a lot of time under the eaves of my porch floor and it is in an area I can't get to (can't even fit to crawl in there when there is dry (no snow conditions). What I usually did (summer and fall) was to hose it down and hope it would dry before they decided to go through or spend time there again. It's a pass through behind my mini split compressor, which I have a screen in front of to block drifting snow and I think they like that there is an entrance and an exit, so they can go through a tunnel like area but have 2 exits. I suppose I could block it off but if I do they'll miss their safe spot in the protected area of the yard where they can still get plenty of sun when it's out. I put layers of straw down and it has gotten pretty damp and the top only really dries out on part of it when the sun is out all day. Their fenced run is fine and although the coop is a bit damp underneath, my plan is tomorrow when it is warmer (in the 50's), to change everything and start again with a clean tarp and bedding. I have the herbal parasite wormer. I guess I'll start that. He has started not to keep his feathers on his tail as white either. Very not like him. Both of the girls (one has had wet feather since I got her early last fall - people tried to help me with that but basically it's just as bad, as she has never used her oil gland) look like their tail feathers have been somewhat stripped and I have not witnessed how that happened so I don't know if that could somehow be related.