There were two screech owl visits to the nest box last night, December 26/27, 2012.
In the first visit, at 1:54 AM CST, Mme. Owl gives herself away by briefly kicking around the bedding material, which is a classic female screech owl behavior: making a depression for her eggs (even though there shouldn’t be any until March).
The second visit is more interesting, because it demonstrates the all-year utility of nest boxes to the owls: one of the owls stops by to deposit a dead mouse for safe keeping, i.e. later eating. This prey caching behavior is normal, and, while all manner of locations may be selected as caches, a secure cavity like the nest box would have to be somewhere around the top of the list. And that is one of the reasons I invariably tell people who ask “when should I put up my screech owl nest box” that the correct answer is always: “now.”
In this particular case, the nest box will be functioning like a freezer, as the thermometer on the wall clearly shows a temperature in the mid-twenties, fahrenheit; significantly colder than predicted. I went out shortly after this visit finished, and rapidly made two observations: the first was a screech owl perched on a tree limb about ten feet from my back door (after looking away for a moment, it was gone), and the second was that the thermometer was correct.