American peregrine falcons have a body length of 16-20 inches and a wingspan of 36-44 inches.

Peregrine falcons are strikingly beautiful. Adults have bluish slate gray backs and wings and whitish below with dark barring on the legs and belly. The black feathers of their head and neck form a feather helmet that covers their eyes and cheeks.

The peregrine falcons preferred habitat is open country near cliffs.

Peregrine falcons prey on other birds and almost always catch their prey in flight. They have tremendous speed during their chase—they fold their wings close to their sides and enter into a dive. The peregrine kills its prey by overtaking it in mid-air and either striking it with fisted feet or grasping it with sharp talons. This diving technique allows the peregrine to reach speeds of up to 200 miles per hour, giving it the reputation of being the world's fastest animal.

The introduction of pesticides into the food web was largely, if not exclusively, responsible for the populations of peregrine falcons becoming endangered. Pesticides sprayed on agricultural fields were consumed or absorbed by plant-eating insects. Small birds ate the insects and peregrines ate these birds.

The pesticides did not always kill the organisms as it passed through the food chain, but the poisons did build up (concentrate) in the organisms' fatty tissues. Once the peregrine ingested the concentrated pesticides, they caused the shells of the falcons' eggs to form so thin, they would break when the adults attempted incubation.

In very recent years, pairs of peregrines have been found breeding on the lowlands near Puget Sound. Bird watchers regularly see peregrines in winter along the Puget Sound coast. Skagit, Padilla, and Samish Bays are examples of areas on the coast where they feed on ducks and shore birds.