It's possible that the owl is there more often but just not visible; as the hollowed section appears to drop deeper into the tree. We've never approached the tree to look inside, as we don't want to chance disturbing it.
I'm posting images from yesterday and the previous 5 years. Not sure if it is the same bird each year, or just coincidence that different Gray Morphs use the same eye-level hollow every year.
Gray Morph Screech Owl shot with Olympus EM1 Mark III and Olympus 100-400mm at 400mm.
Gray Morph Screech Owl shot with Olympus EM1 Mark III and Olympus 300mm.
Gray Morph Screech Owl shot with Olympus EM1 Mark III and Olympus 300mm.
Gray Morph Screech Owl shot with Olympus EM5 Mark III and Olympus 300mm.
This image was shot just after sunset and was taken using high iso.
Gray Morph Screech Owl shot with Canon 7D M2 and Canon 500 F4.