This is not a sparrow spooker – looks like a version of a Noel predator guard. Just Google “Noel bird guard” and it will come up, mainly used for climbing predators I guess. I really have not seen one or heard if they work. The sparrow spooker looks like Brad’s post on this forum of May 8 under “Behavior Questions” on page 5. They do work, but nothing is 100% guard safe.
A Noel guard is supposed to work on raccoons and cats, on the theory that the raccoon’s/cat’s front leg isn’t long enough to reach the nest if one of these is on the box. They are not 100% effective but with this box where it is, it’s better than nothing.