Once you feel you've gotten the immediate problem (numbers) under control, plant mint around your coop and run. Rodents HATE mint and will avoid it. Since even the roots are minty, they won't tunnel either. It's not harmful to chickens or other pets, so you don't have to worry like you do with poisons. And it has many culinary uses. It spreads rampantly and quickly, so you don't need a lot to start with. Has worked like a charm for us. Certainly can't hurt to give it a try.
Good luck.
Good luck.