Peregrine Falcon (peregrines) is about 36–48 cm in length and has 85–120 cm wingspans. The most widespread large falcon of is significant size differences between races. The largest females of northern race calidus are as large as the smallest male Gyrs, southern race brookei is hardly bigger than Barbary.
The most widespread (nominate) race averages a little smaller than Lanner. Hence, it is powerful but very agile in flight, often making long and dramatic, near-vertical stoops (with wings virtually closed) in pursuit of medium-sized birds.
Peregrine Falcon wing beats are a little slow, stiff, and rather shallow in traveling flight, but faster and deeper when in pursuit. Holds wings flat when soaring, with hands slightly upturned. It has a characteristic compact flight silhouette (shared with closely related Barbary). The wings are broad-based, but the hand is narrow and tapers sharply, creating an almost triangular shape when wings fully extended in soaring.
Moreover, the wingtips are sharper than in other large falcons, and the tail distinctly shorter. Peregrine Falcon adult may be separated from other large falcons (apart from Barbary) by this distinctive structure and also (except in calidus) by all-black crown and nape, dark bluish-gray remainder upperparts (with paler area from the lower back to uppertail coverts).
It is a very broad dark moustache (contrasting with clean white cheeks), and extensive barring on underparts from lower breast to undertail coverts (but note that adult dark- and gray-morph Gyrs are barred on flanks and ‘trousers’). Underparts mostly look gray at a distance, contrasting with whitish upper breast and throat.
More problematical is large and pale race calidus (breeding Lapland eastwards, wintering south to N Africa and the Middle East), which has paler upperparts and which can suggest Lanner (q.v.). Also, the confusion between Peregrine and similarly short-tailed Eurasian Hobby is possible at a distance when size and plumage detail is not apparent, but Peregrine is much broader in the chest, has a broader base to wings, and is paler below (with pale breast). See also Barbary Falcon and Merlin.
Juvenile still has characteristic jizz of adult, but plumage differences are less marked (and juvenile calidus often shows Lanner-, Saker- or Gyrlike characters). For differences from Eurasian Hobby or Eleonora’s, Lanner, Saker, Gyr and Barbary Falcons see those species. (Note: all identification pitfalls associated with calidus apply equally to very similar vagrant race tundrius.
The juvenile differs from the adult in being entirely blackish-brown above (not bluish-grey, with paler area from the lower back to uppertail coverts). Underbody tinged yellowish, with bold dark, longitudinal streaks (not bars) from breast to undertail coverts. Also have a small buffish nape patch, finely streaked cheeks, narrower dark moustachial streak, pale supercilium, and paler forehead. The cere and legs are bluish, not yellow (but feet occasionally yellow).
Peregrine Falcon call is usually silent except near the nest, where the most frequent call is a loud, harsh, scolding ‘ka-yak, ka-yak, ka-yak…’, becoming a shrill ‘kek-kek-kek…’ when alarmed. And the adult bird is giving two distinct sounds, creaking and wailing calls are heard.
The wailing call comprises long continuous vocals of ghiiii-ghiii-ghiiii, when they are looking for a mate or sometimes annoyed and don’t feel like good getting up to deal with it. Few Peregrine falcons mate for life or the pair-bond is rooted deep.
The moderate five races including (probably this race) are vagrant tundrius from N America (nominate race and brookei illustrated). Northern calidus is slightly larger than the nominate race and paler overall, with less heavy barring below and a narrower moustachial streak.
The juvenile is paler overall than nominate race juvenile: usually less heavily streaked below and paler brown above (often contrasting with darker flight feathers); may show paler (and more contrasting) feather fringes to upperparts, more prominent whitish nape patch, paler forehead, whitish supercilium, and narrower moustachial streak, thus recalling Gyr, Saker or Lanner (q.v.).
Southern brookei is smaller than the nominate race, darker above with a dull rufous patch on the nape (sometimes extending to the crown), and more pinkish-tinged below with denser barring. The juvenile is darker and more heavily streaked below than the nominate race juvenile and with a more rufous nape patch. Race madens of Cape Verde is browner than the nominate race above, with strongly rufous tinge to crown and nape and pinkish suffusion to underparts. It is resembling smaller but paler Barbary, q.v., of which it may in fact be a race rather than a race of Peregrine). Vagrant tundrius is very similar to calidus and the same identification pitfalls apply.
Generally scarce, however in addition to mapped range, has bred in Belgium, Netherlands, Denmark, and Israel). It breeds on cliffs and crags in hills, mountains, moorland, sea coasts and, in the far north, on the ground or in trees in extensive bogs; rarely, on tall buildings. In winter, also open lowlands and especially estuaries and other wetlands. In order to attract falcons, you have to place feeders and entice the birds that they like to feed on. A fast falcon diving speed is around 390 km.