Chickens sometimes eat mice. I had one die from poison from a mouse that she ate

So far, knock hard on wood, mine leave them alone. I've watched them stand over a dying mouse with their heads cocked making little alarm sounds, me ready to tackle anyone that grabs the mouse. But they walk away from them. I don't know if they somehow sense that something ain't 'right' about them or what.
I also police the area regularly. The Tin Cat bait holders secure latch and work on a 'teeter totter' method where the mouse enters through a little opening, runs up the ramp, the ramp goes down and they can only go one way, into the trap. Can't exit once they are in. The bait is in the holding area so once they eat it they can't get back into the coop.
The trap is then carried out to the road where I open it near our garbage dumpster or in the road. Mice leave but don't survive.
I have mine bungee corded just to make sure no accidents happen.
So sorry you lost a bird to poison. I live in fear of that but there aren't any options left for us. The shed needs replaced. But even in the second room we put in without inner walls the Danged mice found a crack in the floor and tunneled in. I am still filling cracks with concrete patch. It's a never ending battle.
One of our older dogs got ahold of one of our tom cat bait holders and tried to chew her way into it. She didn't. It lived up to it's guarantee but we still had to treat her with vitamin K after doing the wonderful peroxide induced Mount Vesuvius imitation. Not pleasant for anyone involved and especially not for her.
I learned to get crafty with them after that.