Vision is the dominant sense of nearly all birds. In most, the eyes are placed so far to the side of the head that they have mainly monocular vision, meaning that each eye scans a Separate area. This feature is shared by all hunted creatures who depend on vision to warn them of possible danger. Birds of prey and owls have eyes set more to the front of the head, offering a wider angle of binocular vision, which is vitally important for judging distance. Birds also have a third eyelid which moves sideways across the cornea and keeps it moist without interrupting their vision.
Accuracy is crucial for a hunting bird like the eagle which relies on its keen eyesight, first to spot the prey and then to catch it. The eagle’s eyes are therefore positioned sufficiently far forwards to give it binocular or three-dimensional vision.