Birds and their Eyesight

http://www.webexhibits.org/causesofcolor/17B.html

I read the above article about birds and how they see colors and their eyesight, and I learned the following:


1. Some bird species can see ultraviolet light.

2. While humans are trichromats (perceive 3 waves of light), birds and fish are tetrachromats or pentachromats (perceive 4 or 5 waves of light), allowing for them to see more types and rays of light.

3. Bird's eyes have a far higher proportion of cones to rods than human eyes, and their cones are more complex than ours. The inner portion of the cone contains a colored oil droplet behind the outer portion of the cone, allowing for light to be filtered before it reaches the visual pigments.

4. The structure of a bird's retina is also more complex than the structure of a human's retina. The area where there is a high concentration of cones (which perceive light) may form a lateral stripe instead of being centered in one single area.

5. Birds use their vision in different ways, such as using it to differentiate the greens of the forest from their food, or using their ultraviolet vision to spot the traces of their prey (such as the urine and feces of mice).