A friend of mine and I rented this old woman's back yard for the horses one year. There was on old dairy barn on the ten acres that we took days cleaning out so the horses would have shelter. The problem was mice. I have never seen so many mice in my life. You could watch ten of fifteen of them running across the beams while you were in the barn feeding the horses. It was GROSS.
Honestly, my daughter and I would 'trap' some by putting a handful of grain in a trash can and leaving it under a beam over night. By mornign there woudl be between four and 20 mice in the can....
I tried the pound, but because I didn't live there, they were not interested in adopting to us. What I found was a very nice lady who had watched a feral cat have kittens in the brush under in window at work. When the kittens were about five months old, she trapped them, had them vetted, neutered/spayed and gotten them shots of worming. At that point, she looked for a home for these 100% feral four cats.
It was a perfect situation. We kept them in a large dog crate for two weeks, with lots of dry cat food. Then we opened the crate, keeping the cat food dish full, and offered canned every few days.
After a month, they stopped eatign the dry cat food and we removed the dog crate.
We woudl see glimpses of them every once in a while, but the best part was that the mouse population plumited over the next year! There was no more listening to them running across the roof and I never saw one again (well, at least not after the cats had been loose for a coupel weeks.) When I woudl get a glimpse of the cats, they were FAT and SASSY!!!
I did feel bad about leavign them when we left, but they had more than enough wild food to catcha and were doing great.