Owls will eat other birds. In any owl box, you’ll see the remains of songbirds that were taken for dinner.
Maybe they could put used cat litter here and there on the ground; I’ve always heard that will discourage rodents.
Collateral damage.
Best way to catch and kill aviary rats is to hang up bird nest boxes and leave corn shucks on the ground.
When you see corn shucks sticking out of the nest box hole during the day, you have rats nesting in the box. Slap clear tape over the hole, peek inside to confirm no birds, then drop the box in a half filled 55 gallon drum and submerge for 15 min, or run exhaust pipe into it. Will catch a lot of rats at once. Kills them faster and easier than individual trapping.