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Day 3A: The Eyes Have It

Look carefully at these tiny birds. Notice how huge the bulges are where their eyes are hidden. Bird eyes are ENORMOUS compared to their heads. Once the eyelids grow in, they will cover all but a small round part of the eye. Look at a partner's eyes. Our lids open in an oval-shape. We can see the pupil, iris, and a lot of the white part. A bird's eyelids open in a round shape. We can only see the pupil and iris.

Q: Why do human eyelids show more of the eye than a bird's eyelids show?
(Answer under photo.)

Photo: Dorothy Edgington

A. Human eyeballs can turn and roll to see up and down and to both sides. Our eyelids are shaped as they are so our eyes can still see when they move side to side. When birds fly, the rush of air can dry their eyes. To protect them, the lids cover as much of the eye as possible. Also, bird eyes can't roll like our eyes do. Because their eyes are much more "fixed" in the socket, there's no need to have eyelids that allow them to turn from side to side.