A 5 gallon bucket, about 1\3 filled with water and enough sunflower seeds to cover the surface of the water. Provide an access ramp, mice jump in thinking its a bucket full of seeds and don't come out.
I wouldn't leave it out where the chickens can access it, but its easy enough to set it out at night when you close the coop and put it away in the morning when you open. I have way too many animals to use poison or snap traps, the bucket does a good job.
What a great idea! I wouldn't doubt that there are mice and rats around my place, although I haven't seen any signs. I'm saving your instructions in my chicken files in case I do need a trap in the future. Thank you!