That's what I'm afraid of! Trying to keep the mice away is like shifting deck chairs on the Titanic. Get one place done and the little suckers pop up somewhere else! Our coop is up against a shared fence, and the mice are coming from over there. Not much I can do about the other guy's yard, but we are filling in holes, adding barriers and setting traps on our side. I'm hoping eventually the girls will peck at the mice and chase them instead of the mice scaring the girls! We changed their feeder so that they don't spread as much crumble around, but you are right. They drop it everywhere. I have squirrels nosing around, too, but they can't get in at all. Maybe traps are the way to go, although I don't relish the idea of disposing of "full" ones.Re rats and mice in the coop and/or run. Removing food at night and using rodent proof feeders is a start, but I think what's been forgotten is that every grain of chicken food does not either remain in the feeder or in the chickens. Chickens scatter it. They drop it. They bill some out. They don't always find every scrap of food or scratch tossed in. It gets lost in the litter. And those tiny missed bits are all it takes to feed a hungry mouse - they don't need a feeder full....
The most important thing is to try to keep them out in the first place, and that's easier said than done! They are ingenious, survival-driven little critters who will find and exploit every teeny little entry point they find. We use 1/4 inch hardware cloth around the perimeter of our entire setup - it runs 2 feet up the sides and almost 2 feet outwards at the bottom. We chose that because I'd read that a mouse can get through a space 1/2 wide so I wanted something finer. It's secured with screws and washers, wire, and landscape fabric staples (in the ground) and we even put a rubber gasket at the bottom of the people doors to seal any gaps. I thought we'd done what we could.
Last night I went out because I left the water running on the garden. I shined the flashlight on the run as I was on my way out there just in time to see a mouse use the 1/4 inch hardware cloth like a ladder, scurrying up the wall and then dropping down into the run. AAACKKKK!! This morning Ken and went out and bought 8 of those black covered traps. The lady at the hardware store looked a little heebied-out at the thought of what our house must be like so I said, "They're for the chicken coop." She kind of laughed and said, "Good luck. I never did get rid of them completely in mine." Oh, boy. <sigh> But we'll set the traps tonight and put a few inside and the rest around the perimeter and hope for the best. I don't want to use poison because if a chicken finds a poisoned dead mouse she may well think she has a new treat and eat from it. No thanks! Wish us luck!