Falcons are characterized by long, narrow wings and streamlined bodies. The endangered Peregrine Falcon is the same size as the more common Prairie Falcon. Adult peregrines are slate-gray above; the underparts are cream-colored with dark barring. The head is dark with a broad black mustache below the eye. Immatures are dark brown with heavy streaking on the breast and belly. A peregrine ranges from 14 to 20 inches in length and has a wingspan of up to 41 inches. The male is only about two-thirds as large as the female. This species normally ranges in weight from one and one-half to two pounds.

The Peregrine Falcon is found all over the world. In North America it formerly occurred throughout the continent. It inhabits narrow canyons and rugged mountains, and is frequently found near bodies of water preying upon water birds. The population in North America suffered tremendous losses leading to the peregrine's listing as an endangered species primarily because of pesticide, especially DDT, contamination. Peregrines were de-listed in 1999. They can frequently be found in urban settings, often occupying the ledges of high-rise buildings, from which they can swoop down upon unsuspecting prey. Their prey throughout the West includes a variety of birds.

The nesting cycle of the peregrine begins in early March with the birds’ arrival at the breeding territory. Peregrine Falcons almost always return to the same site each year. They do not construct stick nests, but instead create a depression in a pothole or ledge on a cliff. Old stick nests of hawks and ravens are also used. Four or five eggs, white with reddish-brown blotches, are laid in late March or April. Hatching occurs after about 32 days of incubation, the duties of which are performed predominantly by the female. The young falcons grow rapidly and make their first flight at about 40 days of age. The juveniles continue to rely on their parents for food for another four to five weeks after fledging. Most peregrines do not begin nesting until they are two years old, frequently returning to nest near where they were fledged.

Migration of the Peregrine Falcon is quite spectacular, with some birds flying from Alaska to Argentina, a round trip of 15,000 miles. Southern birds probably migrate only short distances and some may not migrate at all. These falcons are observed migrating along western ridges mostly in late September and early October, returning north in late February and March.

Populations of the Peregrine Falcon have slowly been increasing through active preservation efforts and captive breeding programs. Threats still exist, however, because many harmful pesticides are still used outside of the United States where most peregrines and their prey spend the winter. Pesticide contamination remains a serious threat to their survival.