Twice within the past week or so, first thing in the morning, two of my hens in a separate coop with a smaller roo, have come up with a tiny mouse for breakfast. I don't know if the mice were drowned in the drinking water (doubtful) or if they scored the little pest on the ground. I just caught them fighting, chasing each other for dibs on the first course of the day. Do chickens eat mice?!!! Oh yes, the winner pecked at it a little bit and swallowed it whole.