I saw the owl again today! It was fighting with a hawk. Well actually, the hawk was fighting with the owl. The owl was mainly ignoring the hawk.
I heard the hawk screeching, constantly and really loud like it was right outside, so I went outside to look. The hawk was up in a tree over the house, just sitting there screeching. Then it flew a short ways towards a branch that I couldn't really see, seemed like it tried to land, flapped its wings a lot, then shot off in the other direction to another high branch. I walked around and what do you know, the owl was sitting where the disturbance had been. The owl never made any noise, but it moved to another branch a couple of times and the hawk followed it, each time finding a close perch and screeching over and over at the owl. Finally the two of them flew off together.
I wonder what they were fighting about? Who gets first dibs on all the juicy rodents in the yard? Or maybe one was threatening the other's nest. It's the wrong time of year for that, isn't it? I thought owls had their babies in late winter/early spring.
I just googled "owl fighting with hawk" and found your post. I saw a barred owl squabbling with a Cooper's Hawk today. This was in Minneapolis. I also wondered what they were fighting about. I watched them for a long time. It was exactly as you've described your owl/hawk fight.