<P> Apart from its greater size, the common raven differs from its cousins, the crows, by having a larger and heavier black beak, shaggy feathers around the throat and above the beak, and a wedge - shaped tail . Flying ravens are distinguished from crows by their tail shape, larger wing area, and more stable soaring style, which generally involves less wing flapping . Despite their bulk, ravens are easily as agile in flight as their smaller cousins . In flight the feathers produce a creaking sound that has been likened to the rustle of silk . The voice of ravens is also quite distinct, its usual call being a deep croak of a much more sonorous quality than a crow's call . In North America, the Chihuahuan raven (C. cryptoleucus) is fairly similar to the relatively small common ravens of the American southwest and is best distinguished by the still relatively smaller size of its bill, beard and body and relatively longer tail . All - black carrion crow (C. corone) in Europe may suggest a raven due to their largish bill but are still distinctly smaller and have the wing and tail shapes typical of crows . </P> <P> In the Faroe Islands, a now extinct colour - morph of this species existed, known as the pied raven . </P> <P> White ravens are occasionally found in the wild . Birds in British Columbia lack the pink eyes of an albino, and are instead leucistic, a condition where an animal lacks any of several different types of pigment, not simply melanin . </P> <P> Common ravens have a wide range of vocalizations which are of interest to ornithologists . Gwinner carried out important studies in the early 1960s, recording and photographing his findings in great detail . Fifteen to 30 categories of vocalization have been recorded for this species, most of which are used for social interaction . Calls recorded include alarm calls, chase calls, and flight calls . The species has a distinctive, deep, resonant prruk - prruk - prruk call, which to experienced listeners is unlike that of any other corvid . Its very wide and complex vocabulary includes a high, knocking toc - toc - toc, a dry, grating kraa, a low guttural rattle and some calls of an almost musical nature . </P>

How to tell the gender of a raven