This appears to be two birds caught in the middle of fighting, not mating (I am fairly sure that owls mate from behind, like all other birds that I'm aware of). Could be a territorial dispute that took them to the ground. Whatever they were doing, what an incredible sight for you!

That might explain the thumping sound I heard as if someone was falling off the roof, or banging into the side of the house.

It's funny because they actually looked for a minute like two brothers who had been caught in the act of pummeling each other. It was just so odd to see them not moving for so long.

It will definitely go into our Wow, can you Believe we really saw That file!

I am envious about the great horned owls - enough individuals to have territorial battles! I have barred owls in my yard but haven't seen or heard any other species. Hearing just one great horned owl would be enough for my Wow! file.

well, it took me quite a while to figure out where the gallery was, but that is a cool picture. What a sight! It does look like they are fighting. We are studying owls in the kindergarten I work in. I have a ton of owl web sites, so I'll look it up for you, but I don't think it is mating season.