Much easier to judge size in a zoo (I've made my share of size-judgement mistakes in the wild), but this is another eagle owl, specifically spotted, Bubo africanus.
All scops and screech owls have a rather different jizz, appearing proportionally larger-headed and shorter-tailed (compared to wings). Anyhow, I found Queen Elizabeth to be among the most enjoyable reserves in Uganda (2nd after Bwindi) and you evidently had a nice trip too.
Really? I thought it would be spotted (like the illustration in my field guide), and there were four of them, and they all seemed quite happy to sit in the same tree together.
I'm really beginning to dislike owls. At least I'm fairly certain about the third one I saw (photos soon).