Peregrines are large falcons, The females are considerably larger than males. In the case of the Peregrine, the female is roughly 20% longer, and at least a third heavier than the male. Plumage differences between males and females are minor. Males tend to have a slightly whiter breast and somewhat fainter barring on the belly, while females often are slightly browner on the back.

All Peregrines have a hooded appearance, with a dark crown and neck, as well as a moustache (malar stripe) of the same colour on the face. The size and shape of the moustache is slightly different on each Peregrine, and allows individuals to be identified much like fingerprints of humans.

Peregrines are dark on the back, and usually have a light breast and a heavily barred belly. In flight, their dark underwing is often noticeable. Adults have bright yellow feet and a mostly yellow beak and eye-ring, while immatures have pale yellowish-gray feet and a bluish beak and eye-ring. Juveniles also generally have rather brownish plumage on their backs, in contrast to the adults which are gray or black.

Worldwide scientists have recognized twenty-two races of the Peregrine Falcon. (Falco peregrinus).

Peregrines hunt and eat other birds and are famed for their speed (stooping, or diving, Peregrines have been clocked at speeds of up to 220mph) and aerial prowess.

Measurement details:
Length:
male: 37-41 cm (14-16 inches)
female: 42-46 cm (16-18 inches)

Wingspread:
male: 94-100 cm (37-39 inches)
female: 102-116 cm (40-46 inches)

Weight:
male: 453-685 grams (1-1.5 lb.)
female: 719-952 grams (1.6-2.1 lb.)

Voice:
The Peregrine has a harsh resounding "kak-kak-kak-kak" call. Both sexes give the same call, but males tend to sound somewhat wheezy and high-pitched, while females are more grating and coarse sounding. This call is usually given as a response to disturbance. A much softer "ee-chup" vocalizaton is given during courtship, and when birds are together at the nest. Young Peregrines have a higher pitched, more whiny quality to their call, and often vocalize persistently, especially when trying to attract an adult's attention.

Flight:
A Peregrine in steady flight has shallow but powerful wingstrokes, similar to that of a Cormorant. When in active pursuit, the wingstrokes become deeper. When Peregrines soar, they hold their wings flat and fan out their tail fully, making it appear diamond-shaped. While soaring, their wings are fully extended, and the wingtips appear broad and rounded, in contrast to their normally sharp-pointed appearance. In a dive (known as a stoop) the wings are folded in close to the body.