They haven't got it down to a precise hour yet, but raptors do know when it's time to spread their wings and head south.
Experts believe they are able to tell seasons by watching the orbit of the sun. When the sun is just right in the sky, the hooked-beak birds with the steely eyes begin, like many others, their migration to warmer climates.
Flights usually begin in September for most birds. That's why Utah's annual Raptor Watch Day is being held Saturday.
It will be at one location this year, on the Squaw Peak outlook along the foothills east of Orem/Provo. The Squaw Peak road, a few miles up Provo Canyon, heads south. Follow the road for about four miles to the outlook.
Bob Walters, watchable wildlife coordinator with the Utah Division of Wildlife Resources, will be on site, along with several other officers, to help identify birds, answer questions and deliver interesting facts about them.
The family of raptors includes harriers, vultures, eagles, hawks and falcons. Typically, there are a larger number of raptors flying at this location at this time of the year.
Also, points out Walters, "Fall colors will just begin to flirt with the eye, temperatures at higher elevations watch sites will be crisp and, with any luck, clear skies will offer up-close glimpses of the birds."
Those planning to visit the site should bring binoculars or a spotting scope, although officers will have some binoculars available.
Raptors have, for a number of years, been among the true celebrities of the airways. They are the stars on stage every time they fly. They are the birds people like to watch.
In flight, there are few more graceful than raptors. Close up, there are none more fearsome-looking. There has, over the centuries, been a real fascination for raptors, especially hawks, eagles and falcons.
Consensus is that the birds draw the attention because they are a charismatic, attractive bird.
It is not at all surprising that the birds draw the attention they do. It is somewhat surprising, however, to learn little is known about raptors. All of the things that make them attractive also make it difficult to study the birds.
They are elusive, mysterious, secretive and hard to get close to. They are much easier to be spotted flying and in some cases will fly relatively close to where a watch-site has been set up.
One interesting fact, for example, is that not all hawks are hawks, but in some cases, like with the red-tailed hawk, are members of the buzzard family.
There are, in fact, only three true hawks in North America. They are the northern goshawk, cooper's hawk and sharp-shinned hawk. The goshawk being the larger of the trio and the sharp-shinned the smaller. All three birds fly the updrafts here in Utah.
One noticeable difference among the three hawks is that the female is the larger of the species. In some cases, in fact, almost twice the size of her male companion. One theory as to why the female is larger is that her size allows a larger prey base and therefore a broader food supply.
It is known, too, that hawks range from Alaska to the lower 48 states and down into Mexico.
For information on Raptor Day, call Walters at 583-47771.