birdsoup

At the EagleFest children often ask about how well can an eagle see.

The terms “eagle-eye” or “hawk-eye” are often used to describe exceptional vision.  There is much truth (and science) to the belief that raptors have much better vision than humans.  A red-tailed hawk is said to be able to spot a mouse at a distance of one-half mile or more.  I can’t do that, even with binoculars.

All birds have good vision.  They have to in order to survive.  Birds do not have a good sense of smell, so they must rely on sight to find food and to spot a potential predator or other dangers.  Not only are their eyes large compared to their overall body size they have greater image gathering ability.

It’s impossible to know for sure what the world looks like to an eagle, but we know from studying the anatomy of their eyes that their view must be enlarged and magnified compared to our view. Eagle eyes are the same size (weight) as human eyes (though a full grown adult Bald Eagle weighs no more than about 14 pounds!) But an eagle eye has a much different shape from ours. The back is flatter and larger than the back of our eye, giving an eagle a much larger image than we can see. And its retina has many more concentrated rod and cone cells-the cells that send sight information to the brain. Some animals, including humans, have a special area on their retina called the fovea where there is an enormous concentration of these vision cells. In a human, the fovea has 200,000 cones per millimeter, giving us wonderful vision. In the central fovea of an eagle there are about a MILLION cones per millimeter. That’s about the same number of visual cells jammed into a square millimeter as the finest computer monitor has on its entire screen when set at its highest resolution. 

While there is no official eye exam for birds, they do have superior vision to human.  When you go birding, you can be sure that they will see you before you see them.