Since an owl cannot move its eyes around like a person can, it has to turn its whole head in order to look in another direction. Owls have many more vertebrae in their necks than people do. The neck bones are so flexible, that an owl can turn its head almost all the way around.
All birds have flexible necks. Even the little sparrow has twice as many vertebrae in its neck as a person has. A flexible neck is important. It enables the bird to look in all directions for danger, to catch food more easily, and to reach any part of its body with its beak.–Dick Rogers