When I worked for the local branch of the Forest service, we had problems with areas of newly planted beech trees being devastated by mice.
Since the FS aren't allowed to use poison, I suggested setting up a lot of nestingboxes next to newly planted areas in order to support the natural enemies of the mice.
I talked to Denmarks number 1 owl expert and he had a lot of tips as to where and how, the different species of owls like to nest.
Those are very particular birds.
Our common owl ,the Tawny owl ( strix aluco) prefers to nest next to open areas, no less than 18 feet up in a tree a little back from the open ground, like 2-3rd row and does not like the opening of the box to point west.
He told me about a count, done with a pair of barn owls. The ornithologists had counted the number of dead mice the pair brought home for their youngs in a season. 2500 mice!!!!!!
A pair of owls like that could sure make the little beechtrees safer, so we set up close to 50 boxes in the forest. It was a really nice job, and seing the boxes occupied by owls later made it really rewarding.