Developments to date for 2013:
We have two cameras for the Granite Hills Owl Box, an external camera mounted on a nearby palm tree and an internal camera mounted facing into the box. Both can be set to capture still photos, triggered by motion.
Several weeks back we saw the first evidence of owl visits- brief fly ins.Then the external camera began picking up night time  perching on the roof of the box by two individuals. We've subsequently seen a breeding pair in the box. As of this morning there are two eggs being incubated. The male has been dropping off food nightly and the food seems to be stockpiled when not consumed by the female. At one point a small swarm of bees appeared on camera ( we have a microphone in the box and could also hear the buzzing) but fortunately they seem to have buzzed off. About a week ago I was visually checking the box @0730 and was startled to see one owl perched on a nearby palm tree, and it was being harassed by at least two other types of birds.  This perching in broad daylight lasted about ten minutes after which the owl flew into the palm foliage and the harassment stopped. We have heard that  barn owls mate for life and that breeding pairs return year after year to the same box, but our imaging system isn't high resolution enough to allow us to make certain this years pair is the same as last year's pair.Last year there were four eggs in the box, but only one chick survived ( with a little help- I put some supplemental food into the box with a gadget I rigged)- and if I catch any rodents soon in my garden traps, they may well wind up being a supplemental food source too.
For may years I've noticed cyclical appearances of rabbits in our neighborhood- many individuals nibbling lawns in the spring, followed by scant or no visits by summer. Apparently the owls do prey on them ( we saw them brought to the box and consumed) so one reason for the cycle seems linked to the owl predation.