Look for the adult Peregrine Falcon’s large and long-winged shape; thick and dark “sideburns” or “mustache” markings; barred belly, legs, and tail; black hood and dark gray-blue back.
Prairie Falcons are found only in open areas of the West, are more brown, have dark “armpits,” and do not hunt ducks, shorebirds, and pigeons as frequently as Peregrine Falcons.
Gyrfalcons are larger and much more rare in the continental US than Peregrine Falcons.
Merlins are smaller and more compact than Peregrine Falcons, and have a pale eyebrow while lacking the dark hood and mustache. Also, Merlins’ undersides have more dark brown streaks.
