About ten years ago I began noticing that we were using twice the feed. Went out one night with a light and found plenty of mice. Got a large Grandpa treadle feeder and then a second one. Removed all other feeders. Next I got metal garbage cans with very secure lids to store feed in. These two things put an end to the mouse problems. Chickens themselves are pretty good mouse hunters and fight over them, tearing them apart. Unfortunately, the mice come out at night when the chickens turn into zombies, so you can't take advantage of their hunting abilities unless you give them a mouse in the daytime. Pretty grusome to watch, anyway.