How Owls Rotate Their Heads So Far Without Snapping Their Necks

Most animals, humans included, can only turn their heads so far without snapping their necks or causing a stroke. But owls can rotate their necks 270 degrees---an impressive ¾ of a full rotation---without causing any harm. Owls have unmoving eyeballs, so neck rotation is necessary for the animal to have any sort of peripheral vision. How can owls pull it off without cutting off the blood supply to their brains?