It is an unfortunate fact of life that if you keep animals in your backyard you are going to attract rodents. It doesn’t mean your farm is dirty or that you are messy, rodents are just everywhere and if you provide things like shelter, food, & water they are going to gratefully accept your hospitality. They will move in, build a nice nest and raise a family. Before you know it, the rodent population will be out of hand. It can be hard to eradicate an established population, but there are lots of things you can do to keep it from getting to that point.
Regularly inspect your coop
When you are at the bottom of the food chain, you evolve lots of tactics for evading predators. One of the traits rodents have developed is the ability to squeeze into very tiny spaces. The average full grown mouse can squeeze through a hole the size of a dime, a full size rat can fit through a hole that is only an inch across (a little bigger than a quarter). And those are the adults, so smaller adolescent ones can get through even smaller holes!
Inspect your coop regularly for holes or gaps. They have very sharp teeth that can enlarge a tiny gap really quickly, so it’s best to fill in any holes as soon as you find them. I would suggest when making the repair you first cover the hole with strong hardware cloth or metal sheeting, followed by a wood board to patch it. Once they find an entrance they are going to be back frequently and will tell their friends so if they are already getting in at one point you want to be sure they can’t chew their way back in.
Build your coop on stilts
Having your coop raised up a couple feet off the ground gives them less points of entry. Yes, they can climb pretty well, but it’s much easier to chew a hole through wood that is sitting on the ground than one that is 2 feet in the air.
Cover vents & windows with hardware cloth
Rodents can easily bend chicken wire into a hole they can squeeze through. Be sure all ventilation holes & windows are covered with hardware cloth screens that are securely attached.
Protect the foundation
Rats like to burrow in the ground to build their nests, so once they find a good food source, they will want to build their nest nearby. Digging under the coop is the perfect location for them. Around the perimeter of your coop, dig down two feet and bury hardware cloth. This is helpful to do for both raised coops and large coops (like sheds) that might be resting on a few concrete blocks as a foundation. If your coop is very large and has a traditional poured cement foundation it is really unlikely they will borrow underneath. Don’t store firewood piles, scrap lumber or brush around the coop. You want to avoid anything they could use to make their nest in. Keep the landscaping around the coop trimmed.
Collect eggs daily
It isn’t just the feed they are after, they love to eat eggs as well. Collect them often to remove the temptation. You don’t want them eating your eggs, and you definitely don’t want them hanging out and pooping in the nest boxes.
Close your coop at night & don’t leave open feed outside
Rodents certainly can and do come out in the middle of the day, but much of their activity will take place at night. Closing up your coop every night not only keeps your birds safe from predators, but also cuts down on rodents coming in to empty the feed bowls. If you normally feed your flock outside of the coop in the their run, take the feed bowl inside at night when you close them up. Having an unattended bowl of feed sitting out in the run overnight is like having a neon “Eat Here” sign. In the hot, dry summer if you keep your water dish outside you should dump it at night so you don’t attract rodents looking for a drink. Likewise in the winter when liquid water is hard to come by, a full heated bowl of water is just as welcoming as food.
Store feed bags in metal bins
It’s convenient to have extra feed on hand to cut down on trips to the store, but all that extra feed is a rodent buffet waiting to happen. They can easily chew a hole in feed bag and can chew through plastic bins. Get some metal trash cans with tight fitting lids to keep your unused feed in.
Food & water bowl placement
If you feed your birds inside the coop, be strategic about where you put the feed. A feeder hanging from the ceiling in the center of the coop is an excellent placement. Rodents are always on the lookout for predators (and chickens do eat rodents), so they will creep along the walls and just dash out for a mouth of food, then come back to the shadows to eat it. Keeping food along the wall in an open bowl just makes it easy for them.
My ducks have a hard time eating out of the hanging feeders, so I have pushed two pallets together, screwed plywood to the top & covered it with vinyl floor tiles (for easy cleaning). I put this in the middle of the coop with the feed bowls & water bowl on it. Raising it off the ground keeps straw out and also makes it scarier for rodents to get to (image being on a raised stage in the middle of a room surrounded by animals that can eat you while you steal their food!). Try to avoid scattering feed or scratch loosely on the floor of the coop or in the run. Anything left uneaten is just there for the taking.
If you already have an infestation
Definitely keep using the above mentioned prevention methods. Anything to make your coop & yard inhospitable to rodents is a step in the right direction. Poisons are a tempting option, but really need to be a very last resort. Covered poison containment traps are an absolute must when using rat poison to keep your birds from nibbling the poison bait, but your birds could still be in danger. Often a rat will take the poison bait, but go elsewhere to die. If your chicken then finds & eats that dead rodent, they will ingest the poison as well. Even if your chickens don’t get to it, some wild animal will likely eat it eventually and would be poisoned.
Snap traps are a good option, but you need to make absolutely sure that your birds/pets/children can’t access them and get hurt. Your local feed or farm store should sell containment boxes where you can put the trap inside to safely use snap traps.
Many people have success with using water bucket rat/mouse traps. You use a 5 gallon bucket with water and set up a baited roller or flip down cover across the top. The rat/mouse walks on the roller or cover and is dumped into the bucket of water where they drown. If you search YouTube for water bucket mouse trap you will find dozens of tutorials.
If you have the facilities to care for a barn cat, introducing a natural predator is always a good way to keep rodents down. Many shelters have some cats that are not suitable for pets because they are feral, but they can be adopted as barn cats. You can also check with other local farmers to see if they know of someone with a litter of barn cats. It’s best to ask if the cat (or mother cat if you are getting a barn kitten) has any experience around chickens or ducks – you don’t want to get a cat that will also chase after your birds!