I did not think that I had mice yet in my coop but this morning walked in and in the entryway I had an empty 5 gallon bucket. Well I looked in there and there were 4 beady eyes looking up at me. I guess the two little mice fell in while walking around the rim and could not get out.
If you have an area where the chickens can't get to you could make a "redneck" mouse trap. My sister and parents have used this many times and caught everything from mice to rats to squirrels.
Basically it is a 5 gallon bucket half full of water. Place a string across the bucket with a peanut butter covered soda can tied in the middle. When the critters try to get to the peanut butter they either fall of of the string or the can spins and they drop into the bucket and eventually drown.
It is non-toxic and safe. The only issue I would see is if the chickens got into the bucket so that is why I recommended outside of the chicken area.
We found mice on our back patio (our coop is on the side of the house) which really freaked me out. We tried conventional mouse traps and sticky traps and it took a few weeks just to catch one mouse.
Last week I was at Home Depot and I picked up a mouse zapper. It was expensive ($20). But it got three mice, three nights in a row. It actually attracted 4, but one was still alive when we picked up the zapper and when the hubby turned the zapper off and on again, it shocked the mouse but it jumped out, at me
DH killed that one with a bb gun while it was hiding under a plastic storage bin.
Anyhow, for the $20 we got three mice on three consecutive nights. I was going to put it out again, but our dog got to it (she's a lab) and chewed it up trying to get to the peanut butter inside. I'm going to be getting another one though. We easily spent more than $20 on various traps with no/little success, so this is a better deal for us.
Sadly, we've had to use poison to control them. Poison was our last option, but it worked well and fast. First we tried the bait bricks, and the rats carried them away and I didn't find any dead rats, but I noticed a small dip in the population.
Next we bought the pelleted rat feed in the tray you lay out. We put the whole box out, 4 trays total and lo and behold all the rats bit the dust. Big ones, small ones, males and females. I think the pellets work best because one rat can't drag it off and gaurd it, therefore more rats eat from the trays. AND because the tray stays where you put it, you know when the poison is gone and you can stop worrying about the chickens or other animals getting it.
Since we set the pelleted poison out, about a week ago, I've picked up 2 HUGE rats and 4-6 large adults. I'm sure there are more, but these are just the ones that died out in the open.
You might try Mouse Magic repellent by Bonide - a nontoxic repellent made from spearmint and peppermint leaves, or cotton balls dunked in peppermint oil, adocumented mouse repellent. I would keep this stuff away from where the birds sleep as I don't know whether these odors we find pleasing are bothersome to them.
You probably are already doing this, but food should be kept completely inaccessible at night (I use metal containers with weights on top - works great). And do the best job possible of cleaning up any that falls on the floor.
Also, if your set up allows, shore up access to your coop with hardware cloth.
Using a combination of these techniques I do not have a problem. An occasional mouse but that is no threat and does not trouble me.
I do not use poison - it is indiscriminate and can harm unintended victims, whether by them eating the poison directly or by them eating a mouse or rat killed by the poison.
I've tried everything to get rid of the mice in my barn. Nothing worked. Traps, traps and more traps with not one little critter caught. I finally did a search on the net this past Sunday and found a non-poisonous recipe.
It worked better than I hoped. On Monday morning I could smell that it worked but couldn't find any bodies. They must have died in their tunnels.