I put several bales of straw down to cover the mud last spring. I lost 2 hens to impacted crops before I figured out what was going on. I took one to the vet for a necropsy, he mentioned that there was long stuff in her crop. I checked them all as soon as I got home. Treated for impacted and sour crop. Won't ever put straw down again.I bought a silver tarp at harbor freight with a coupon of course the size of my coop/run that covers top and sides. The tarp is sun reflective, waterproof, and snow proof. It’s important that it states all three otherwise it isn’t. $14-15. I’m told straw is great also but putting in dry leaves with current mulch at this time since free and abundant but may switch to straw when cooler here. Little bit worried about straw as saw examples of impacted crop due to straw when chickens tried to eat it. Not sure how often this happens. My girls pick occasionally at their mulch but more or less moving it looking in it for goodies than trying to eat it. Not sure yet about waterer. Read online you can stick water bottle filled with salt, close up tight, and stick in water fountain to prevent freezing. Debating that or de-icer for it.