Q: Why do owls turn and bob their heads so much?
A: Owl eyes are very large. They are so large that they cannot move in their sockets. Imagine having a pair of binoculars up to your eyes and looking straight ahead. If you hear a sound to the side, you can’t see what made it unless you turn your whole head so the binoculars are pointed toward the sound. That’s how an owl sees all of the time.
Without binoculars, you can roll your eyes up or down and move your eyes left or right without moving your head, but an owl can’t. And even when looking forward, owls have a smaller field of vision than people do.
To see what your visual field looks like try this experiment. Hold your arms out with both of your index fingers in front of your nose. While you stare straight ahead, move your arms in an arc toward your sides, still staring forward. When you can no longer see your fingers
stop moving your arms. The arc that your arms made is your visual field and measures approximately 180 degrees.
An owl’s visual field is only about 110 degrees. For an owl to focus well, it must turn its head to get an object into its visual field. In addition, owls often bob their heads up and down to judge distance.
By Dick Brewer