Did you know that hawks can see roughly four times better than humans? Their eyes exhibit a number of peculiarities, one of which stood out to me in a recent presentation by Dan Hart of the America Bald Eagle Foundation (www.baldeagles.org). Raptors have the ability to perceive the near ultraviolet part of the light spectrum (from 320-400nm), which is outside of the visible spectrum for you and me.
This capability is put to work in intra and inter-sexual signalling, navigation, prey identification, the control of circadian rhythms and intraspecies communication. The capability is provided through an additional cone, which sees UV instead of the typical red, green or blue that our cones detect.
Several days ago I was speaking with Luke, a veterinary student at the University of Georgia, and he conjectured that the American Crow is likely the most colorful and bright bird in the sky when viewed through a raptors eyes. Isn’t that an amazing thought? Anything looks different from a perspective other than the one we’re used to!
Another important difference is the raptor’s superior flicker fusion frequency. Humans have a flicker fusion frequency of 60 hz whereas raptors is significantly higher. We see, in essence, more slowly than they do. A television image, for instance, that appears seamless and full motion video to us would appear jerky to them, whereas a raptor would see something much faster, like the flicker of a squirrel tail, would appear seamless to them and blurry to us. Even the incandescent lights we use would appear to flicker to the raptor, like a bad flourescent light would appear to us.
There is so much more to discover about the hawk’s eyes and I will look to post more later if there is interest.