Despite the calm appearance of this photo, what you cannot imagine is the cacaphony in the woods. There was a large group of corvids – both crows bluejays flying in and out of the forest while making a huge din. This went on for several days. Carrion? Territorial wars?
Just a theory but … Ravens (another member of the corvid clan) detest Great Horned Owls and will gang up on one when they find it in their territory. They harass the owl with an annoying call which is unique to owl-harassment.
Just one possibility. Corvids are generally much smarter than us and seem to enjoy harassment – so who knows what passes through their super-brains.