There are different owl boxes for various owls. The Barnowl prefers a closed owl box with an oval entrance hole whereas the spotted eagle owls like an open sided owl box. Do provide them with water and tall trees where they can roost as well as use them as a lookout point to search for food. Owls enjoy rats and mice so don't put out any poison to kill them. If you hear the owl at night you will know that you are privileged as your garden has passed the test!