The Peregrine Falcon (Falco peregrinus) is a medium-sized raptor found almost worldwide. Three subspecies are recognized in North America, but the one you’re most likely to see in the Midwest is the American Peregrine Falcon (F. p. anatum). Its range extends from Alaska and Canada all the way south to Mexico.
Historically in Illinois, Peregrines were documented nesting along the Mississippi River between the cities of Alton and Grafton, as well as near the Illinois and Wabash Rivers in Jackson County. Today, the majority of the current population follows the Lake Michigan shoreline, with an occasional pair found in the Springfield and/or along the Mississippi River. Peregrines are naturally cliff-dwelling birds that build their nests—called eyries (EYE-reez)—on ledges. They lay their eggs in a scrape (a small depression) made in the substrate of the cliff ledge. One egg is laid every 24-48 hours. A typical clutch size is four eggs, but occasionally a falcon may lay five. Peregrines produce only one brood per season but may try to re-nest if their first clutch of eggs fails.
Male Peregrines will assist with incubation though the female does the majority. The incubation periods lasts around 32 days. Once the eggs hatch, the female broods the chicks for the first few days while the male hunts for the entire family.
Unlike hawks, Peregrines don't circle the skies while scanning the ground for small mammals to snatch. Instead, these raptors are aerial hunters, known for the speed at which they can dive on other birds in flight, their primary prey. The Peregrine’s ability to take birds as large as waterfowl led to its being called the Duck Hawk.
Young Peregrines take their first flight when around 40-45 days old. The first 3 weeks out of the nest are spent learning how to fly. Once they attempt hunting on their own, the adults will feed them less and eventually the young disperse out of the natal territory. For our Illinois Peregrines, most of the adults stay in the state year-round.
In raptors, females are larger than males. Female Peregrines are called Falcons while a male peregrine is a Tiercel. Young peregrines still in the nest are called Eyasses.