By far the most important sense for a Bald Eagle is its sight. The eyes of an eagle are extremely useful hunting tools. In many ways an eagle's eyes are similar to human's eyes. Like humans, an eagle's eye has a cornea, iris, lens, retina, and an optic nerve. Light goes through the cornea and the lens and projects an image on the retina. On the retina there are specialized cells called rods and cones. Rods are sensitive in poor light and are developed best in nocturnal animals. The cones detect colors and are used during the day when there is plenty of light. Once detected by the rods and cones, the information is sent to the brain along the optic nerve. Once there, the information is translated into a visual image.

In addition to these vision basics, Bald Eagles have some special adaptations that give them excellent day time sight.

1. The Bald Eagle has a greater concentration of cones as compared to rods. In fact, in some areas of the retina, there are nothing but cones. The greater the amount of cones, the finer the vision and the higher the resolving power. Resolving power is the ability of the eyes to focus on objects at a distance. Being able to see things better at a distance has its price though. Eagles may have many cones, but they do not have many rods. Not having many rods makes it very difficult for the eagle to see in the dark!

2. Eagles and other birds of prey have foveas, which are curved pits in their retinas that contain even greater amounts of cones and a high density of nerves to send visual information to the brain. These ultra sensitive sites actually see objects more clearly and from greater distances.

These two adaptations allow the eagle to see with a resolving power that is 8 times greater than humans. Check out the Classroom Homework so you can see with "eagle's eyes."