When I was searching out photos for my post on animals’ eyes back in November, I became fascinated with the variety of eye shapes and colours. Then I began to look more closely at birds’ eyes. Did you know …
Birds have the largest eyes relative to their size in the animal kingdom.
Excellent vision is essential to birds so that they can avoid collisions and capture their prey.
Birds don’t have as many eye muscles as humans so they can’t roll their eyes around as much as we can. That, plus the fact that the eyes of many birds are set at the sides of their heads, means they have to turn their heads to one side or the other, or bob their heads up and down, to see close things better.
Birds have an extra set of photo receptors within their eyes, called double cones, which, scientists speculate, probably means they have much better colour vision that most animals.
Birds have three eyelids: the third eyelid is a nictitating membrane that moves horizontally across the eye both to lubricate it and to protect it from injury.