A few years ago, I had a 30 gallon metal can in the shop with birdseed in it. Took the last scoop out of it and left the top off, it was up against the wall. Next day there were several field mice in the bottom of it, they couldn't climb or jump out. Light bulb clicked on, and have been using it since. Any kind of feed/oats/corn in a deep enough metal container, only takes a little bit of leftover grain to get them to do the swan dive.
We do that with coons too, but use a 55 gallon drum with a hole cut in the lid and bacon grease for bait.
