American Peregrine Falcon

The Fastest Creatures in Colorado

American peregrine falcons can swoop down on prey at speeds reaching 200 mph. The Peregrin is a medium-sized falcon characterized by a nearly black helmet, a dark slate-blue back, and buff broken by horizontal bars on the underparts. Adult peregrines vary in length from 15 to 22 inches, with a wingspread of 43-46 inches. Female peregrine falcons are slightly larger than the males, and weigh between one pound 14 ounces and two pounds 11 ounces; males average one pound seven ounces. Like all falcons, it has long pointed wings and quick steady wing beats in flight. There are two subspecies of peregrine falcons – the American (anatum) and the Arctic (tundrius). Arctic peregrines migrate through Colorado. The American breeds and nests here.


The Latin name, peregrinus, means “wandering” or “coming from foreign parts”. Peregrines have an extensive range worldwide, occurring on all continents except Antarctica. They breed from Alaska and the Canadian Arctic, south through the mountainous western United States and sparingly in the east. Peregrines winter on the coast north to British Columbia and Massachusetts, and in South America. In Colorado, the falcons can be found from the Front Range to the state’s western border.


Summit Lake park from the Summit of Mount Blue Sky

Peregrine falcons inhabit open spaces associated with high cliffs and bluffs overlooking rivers and coasts. Recently, many cities with tall buildings have become home to some peregrines. Some populations are migratory and travel great distances (as their Latin name implies).


Their diet consists of small rodents and small to medium-sized birds. Peregrine falcon pairs may double-team a prey bird, confusing it and making a kill more likely. They often hit them from out of the sun (which makes it easier for the falcons to see and nearly impossible for the prey bird to see them coming). When falcons strike at great speeds, they may knuckle the prey, stunning it, and then circle rapidly around to catch the falling bird in their talons. It is thought that the series of baffles in a peregrine’s nostrils slow the wind velocity, enabling the bird to breathe while diving after their prey.


Peregrine falcons mate for life and territory is established and fiercely defended by the pair. They prefer to nest on high cliffs, although some birds have taken up residence on ledges of skyscrapers in large cities. No materials are used to build the nest. Instead, it is a scrape, usually in loose soil, sand, or vegetation. The pair will return to the same ledge, known as an aerie (‘ar-E), year after year. The female will lay two to six eggs, and she will incubate them for about a month. The young, called eyases (‘I-as), attempt their first flight five to six weeks after hatching. On average, two eyases successfully fledge per nest.

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