Wednesday, April 25, 2012
Birds Can See More Colors Than We Can
Avian vision is pretty amazing. Birds that have eyes on the sides of their heads (such as parrots and songbirds) have a huge field of view. Some, such as the ringnecked dove, can even see almost all the way around their heads. Raptors, with both eyes facing forward like ours, have superior depth perception. Most birds can see rapid movement as well as extremely slow movement - for example, they can detect the apparent motion of the sun as it moves across the sky. There are even studies that show some birds can see magnetic fields! One of the coolest things about bird eyes is that they can see colors we humans cannot.
You may recall from biology class that eyes have light receptor cells called rods and cones. Rods are more sensitive to light in general, and are important when it comes to night vision. Cones don't work well in low light, but are what allow us to see color, detail, and rapid changes. There are different kinds of cones that respond to different wavelengths of light. As you might remember from physics class, red is at the "long wavelength" end of the spectrum, violet is at the "short wavelength" end, and green is in the middle. Humans are trichromatic, which means we have three types of cones - one that responds most to red, one that responds most to green, and one that responds most to blue and violet. Birds are tetrachromatic. They have a fourth type of cone cell that responds to ultraviolet light, which means they can see it. They can probably also see differences between colors that appear identical to us. This is an advantage in finding a mate and in foraging for food.
There's a lot more to an actual "bird's eye view" than seeing something from high in the sky!