Those are all fantastic shots. I have spent a lot of time over the last 18 months or so trying to find owls. Studying where they should be, going to known wintering sites, looking for owl pellets, all with very little success. The only ones I've got photos of were pointed out by others, or captive:
Last Spring at Magee Marsh I was tipped off about this Great Horned Owlet. The Swarovski reps had it in the sights of one of there spotting scopes. I took these with my 55-300 barely being able to see it, it's amazing how it blends in with the tree. It was probably 50-70 yards away, and these are heavy crops.
I was at the High Banks Metro Park in Columbus and a guy on a trail told me where this Barred Owl was nesting, it was only a bout a half a mile away just a few feet off a trail.