Birds, The Real Tetrachromats

Currently, my honors chemistry class is learned about electromagnetic radiation and electron configuration. For an assignment, we were told to read an article about the vision of birds, and how their eyes contrast with that of humans.

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

Here's five interesting facts I learned from reading the article:

1. Humans are are trichromats, having photo-pigments with sensitivities at three peak wavelengths. Birds are in fact tetra- or even pentachromats. They can see four or five peak wavelengths, and sometimes, even ultraviolet waves. It was assumed that only insects could see the ultraviolet waves.
2. The eyes of birds are constructed differently than humans, and definately has something to do with the ability of birds to view more wavelengths. In the eyes, birds have a higher proportion of cones to rods. The oil droplets around the cones in birds, filter out certain light (high-energy lower wavelengths) before it reaches the visual pigment.
3. Birds of all kinds depend on their vision to carry out their day to day activities. Whether they are in the sky and need to locate small animals to snatch up, or find seeds amongst a very green floor full of vegetation, ultraviolet vision is beneficial. With this vision, birds can spot traces left by animals. For birds that prey on small animals, they will be able to guess where their food is. For seed-eating bird, seeds will be easier to spot.
4. The location of the eyes on the birds' heads is different in comparison to humans. Birds like hawks and eagle, whom fly very high and require better vision, have five times more cones than humans do. The spacing in between the eyes when greater, gives the birds increased binocular vision and depth perception. This doesn't necessarily affects the color vision of birds, but it improves the overall visual perception birds have of their environment.
5. The level of vision birds have depends on their life styles. Diurnal birds, active in the daytime, tend to have increased ultraviolet sensitivity. While nocturnal birds, active at night, have increased sensitivity in the infrared spectrum. This may be because they have a relatively higher proportion of cones (mentioned in #2) in their eyes.

These graphs show the differences between the vision of birds and humans in regards to their ability to see "x" amount of wavelengths. (-taken from link listed above)