Went out to check the chickens this morning and had to catch Tootles, my yellow EE chick to check under her wing. I thought she was covered in black bugs, but it ended up just being bits of mud. It's been raining so the ground is wet (altho not muddy), is she trying to dust bath in the wet dirt? Should I provide them with a tub of potting soil or sand or something so she can 'bathe' and end up a bit cleaner rather than dirtier? It was just under her one wing. She didn't look particularly dirty on the rest of her, which is why I thought it was a parasite or something at first.