If you were to stand face to face with an owl, including this Great Gray Owl, it would eventually move its head, bobbing rhythmically from side to side, then forward, then back. Or almost completely upside down. This head-bobbing action helps make up for an anatomical limitation: an owl’s eyes are fixed in position — they can’t move the way a human’s eyes do. The owl’s varied head movements help it judge the position and distance of things around it — essentially, to triangulate on objects, including potential prey. And to build a composite picture of its surroundings.More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.