They can do pretty cool tricks.
Basically, they change their appearance when scared or angry.
In that video, when the owl is put together with an owl that is bigger than it, but not by much, it puffs itself all up.
But when it's put together with another owl that is MUCH larger than itself, it completely changes the way it looks. To me, it almost looks like it's trying to make itself look like a hawk, or some other bird of prey, that maybe most owls wouldn't try to mess with.