That's pretty strange about bird ears. Almost one of those "too much information" things, particularly about the owl's eyeballs.
Many years ago one of my house mates had a cat named Ophelia who was very dainty and delicate. But on summer evenings she would sit on top of her mistress's car and take in the sounds. Her head and her 2 ears acted as totally independent units. The ears swiveled this way and that while the head rotated to it's own plan. It was a site to behold.