There was a screech owl in a brooding posture on the floor of my box a few hours ago. A male would be unlikely to adopt that posture, in my experience, so I assume the owl was a female whose mate must have recently claimed the nest box, and talked her into trying it on for size. (I heard a male in my back yard calling quite persistently one night last week.) She's gone now, but this is an encouraging sign as far as nesting in the nest box this year is concerned.
On the other hand, I saw at least one similarly encouraging visit last year, and nothing came of it, so don't anybody get their hopes up.