Peregrine bird is a powerful medium-large falcon, very adept in the air and agile in flight. While there are subtle sexual plumage differences, a greater difference is the size, the (Peregrine bird) female being 15 per cent larger and up to 40 per cent heavier than the male. The upperparts of Peregrine bird are slate-grey, with a paler blue-grey on the rump that contrasts with the darker, closely banded tail. On the head, the grey of the upperparts merges into the black crown and broad black moustachial stripe, which forms a distinctive black hood. The throat, cheek and remaining underparts are white, and from the lower breast to the vent it is closely barred with black, which may appear grey at range. The female should show a more extensive white breast than the male, contrasting quite strongly with the barred belly, a feature which in both sexes is visible at great range.
Peregrine birds are widespread and are able to utilize a wide variety of habitats, although this is often strongly related to the availability of secure nesting sites. Peregrine bird occurs over all kinds of open country and typically nests on crags and rocky outcrops in moorland and mountainous areas, and also on coastal cliffs. Some pairs will use tall buildings in urban areas, and overall they are very adaptable. Their main prey is small- to medium-sized birds, which are taken on the wing after a chase, often following a very steep and fast stoop with the wings held close to the body.
Peregrine bird mostly silent away from breeding areas, where it can be quite vocal, particularly when disturbed. The most frequently heard call of Peregrine bird is perhaps the harsh persistent "khhe'khhe'khhhe'khhe" or "rehhk-rehhk-rehhk", which becomes faster and shorter when alarmed, such as "kak-kak-kak-kak". There is also a begging "wheeeer-kheeeer-kheeeer...", and another call described as a 'rusty hinge' sound, given in greeting and courtship, such as "ee'Yukh ee'Yukh ee'Yukh" or "ee-chip". A variant on this is used in antagonistic situations, "klee-CHIP" when coming from the male, and "klee-CHUCK" from the female.