Housing And Coop Security
This is not my coop, but isn't it adorable? It also demonstrates the security a coop & run should have. Notice how it's lifted above the ground. This prevents rodents from taking up residence under your coop. It is a solid structure without any holes or loose boards. All windows are covered with hardware cloth fencing. This is important because mice, rats & even weasels can get into your coop through any space larger than 1/2 inch!
Chickens need lots of ventilation! This coop has several windows for good air flow on at least two sides. There are only two things I would add to this coop. First, a vent at the peak. The higher the vent, the more moisture will escape the coop. This is especially important in the winter to prevent frostbite. Also, I would add a lock on the hen box. Without a lock, predators could lift up the top & gain entry to the coop.
The outside run is covered top to bottom with hardware cloth fencing. The hardware cloth should be buried at least 10" along all sides to prevent predators like dogs or raccoons from digging an entry into the run.
Another thing I'd like to point out is the metal garbage can for feed. This a great way to keep from attracting rodents to your coop & run along with not leaving any feed or water out at night.
Rodents
If you have chickens, they will attract rodents no matter where you live. It's up to you to make sure they don't stay. It's important to always put away all food and water at night. If rodents have a constant food supply they will find a place nearby to live & be visiting your run nightly.
Keep all feed in a metal container with tight fitting lid or keep it in the house & bring it out daily. Rodents like rats & snakes will also steal eggs, so you'll want to collect them often. Rodents carry parasites, germs, diseases, fleas & the like. Keeping them at bay is key to good flock health.
With some work you can keep your flock reasonably safe, healthy & happy.