Where and when Rook and Jackdaw occur throughout Britain and Ireland, except in the Scottish Highlands. Carrion Crow is similarly widespread, but is replaced in NW Scotland and Ireland by the Hooded Crow. Raven has been traditionally confined mainly to Scotland, N. and SW England, Wales and much of Ireland. In recent years, however, it has shown a spectacular increase in lowland and even urban areas in the west and has started to spread east (it bred in Kent in 2009). Chough occurs almost exclusively on rocky coasts of Wales (some also inland in the north), the Isle of Man, SW Scotland and Ireland (excluding the east coast). It has recently spread to S. Wales and started to breed again in Cornwall (six pairs in 2010).
Adults Seen well, adult Rook is easily separated from Carrion Crow by its bare, whitish face (the crow has a fully feathered face); Rook also has a throat pouch which, when full, appears as a prominent lump.
Shape and structure Particularly useful when separating crows from juvenile and first-year Rooks (see below). Carrion Crow has a rather flat crown and a low forehead, which merge into a blunt-looking bill to produce a wedge-shaped profile (with the bill appearing as a continuation of the head). Perched, Carrion Crow tends to adopt a pot-bellied posture, with the wings and tail held close together and in line with the body at 45 degrees. At rest, Rook has a steep, even vertical, forehead and a peaked crown, creating a distinctly domed head shape. It also has a ragged, ‘trousered’ effect to its thighs and it often perches with its belly feathers fluffed-out over its legs and feet. A full, rather mobile, rounded tail is often partially spread or pointed vertically downwards. Thus, it often looks angular and ‘disjointed’ compared to the more compact, hefty and menacing crow. In flight, differences are subtle, but Carrion Crow has slightly broader, more rounded wings and a shorter, squarer tail. Again, Rook appears less compact, with somewhat tapered wings that usually have the primaries slightly angled back. The tail appears distinctly more rounded in flight (the wing and tail shapes may lead to high-flying Rooks being mistaken for Ravens). Carrion Crow’s flight is slightly flappier, but differences are slight and depend largely on what the bird is doing.
First-years Juveniles of both species are duller bodied than adults; juvenile crows have a distinct brownish cast to the body plumage prior to their late summer/early autumn moult (as well as a shorter bill, which may initially show extensive dull pink at the base). Their wing feathers remain brownish into their first summer. Note in particular that juvenile Rooks have fully feathered faces and appear crow-like; consequently, they are surprisingly difficult to separate. Only late in their first winter or in spring do they start to lose both the facial feathering and the crow-like wedge of feathering along the top of the bill base. When separating juvenile/first-year Rooks from crows, overall shape is particularly important (see above) and note that their bill is more pointed, less rounded at the tip. At close range, young juvenile Rooks have distinctive blue eyes, but they quickly darken in late summer; also, the bill may show greyish areas even at an early age. Young Rooks are smaller and skinnier than adults and, by late winter, are heavily abraded about the wings and tail (latter often show protruding feather shafts); the growth of new central tail feathers in late winter will briefly accentuate this graduated look.
White plumage Immature Carrion Crows often show white feathering, especially in the wings, which sometimes show a large white wing-stripe. This pigment loss is thought likely to relate to mineral or vitamin deficiencies as a consequence of poor diet.
Calls An important distinction: Carrion Crow has a characteristic caw, whereas Rook has a gruff, strangled aargh. Carrion Crow also gives variations on its call, such as a far- carrying ringing cronnnk and a hard k-r-r-r-r when mobbing a raptor. Both species can make other very peculiar noises, especially when displaying, e.g. Carrion Crow may make loud rattles, reminiscent of a drumming Great Spotted Woodpecker Dendrocopos major.
Behaviour Rooks are, in general, more gregarious, but such differences are not absolute as large flocks of crows are not uncommon (especially in spring). Rooks usually breed in colonies (rookeries) whereas crows are solitary nesters.
Easily separated by its grey belly and mantle, and its black head, breast, wings and tail. Intermediates between Hooded and Carrion Crows are frequent in the zone of overlap between the two species. Extralimital Hooded Crows (e.g. in s. England) should be studied carefully to ensure that they are pure bred.
Compared to Carrion Crow, Raven is huge (wingspan about a third bigger and similar to Common Buzzard Buteo buteo). However, when seen high in the air its enormous size is not always apparent. Shape is significant: Raven is long-winged and (unlike Carrion Crow) the ‘hands’ are rather tapered and angled back. The tail is strongly graduated and looks diamond-shaped when soaring. However, the tail shape may not be obvious at a distance, particularly when closed. It has a distinctly longer head and bill profile, the huge, deep bill projecting conspicuously from the powerful head, the whole effect often emphasised by the shaggy throat feathering. Beware of misidentifying high-flying Rooks as Ravens, their shape being vaguely similar. On the ground, Raven looks oddly short-legged, while the large head and huge bill can make it look somewhat front-heavy; in direct comparison with Carrion Crow it looks massive.
Calls Very vocal, its loud, croaking cok cok and deep argh being diagnostic, as is an evocative hollow, drawn out, ringing kwaark or quonk. It also gives a variety of other calls including a strange ‘song’ that includes peculiar guttural and bubbling noises. Juveniles may give more subdued notes or a higher-pitched kar.
Behaviour Often seen in pairs flying high and purposefully, the female well ahead of the male, the latter often trying to impress her by flipping onto his back with partially closed wings (which enables instant recognition even at great distance). They also indulge in other more spectacular aerial displays, twisting, tumbling or rolling in flight. They may gather in numbers at a good food source and even roost communally (up to 2,000 recorded at a roost on Anglesey). Juveniles Like Carrion Crow, juveniles are duller and more matt-coloured than adults (tinged brown on head and body). In flight, ageing is possible at considerable distance, owing to the fact that adults start to moult their primaries as early as mid April, completing this by late summer. Thus, moulting adults in late spring and early summer show conspicuous gaps in their primaries or a distinct step between their short, newly growing inner primaries and their long, unmoulted outers (which often appear quite strongly angled back). At the same time, juveniles have completely fresh fully grown primaries (but the wings are often slightly shorter than adult’s).
Much smaller than Carrion Crow. Unlikely to be confused at rest because of its short bill, grey nape and whitish eye (until early autumn, juveniles have a darker, slightly browner nape and darker eye). In flight, a small, compact, short-winged corvid, with distinctly tapered primaries and an energetic, flapping flight. Like Rook, it is gregarious, and often associates with that species in large mixed flocks. It has a wide vocabulary, but the familiar, excitable jack jack is diagnostic. It nests in holes in cliffs and trees, and in chimney pots, on which they often perch. Jackdaws with a horizontal white crescent on the sides of the neck are sometimes seen. Such birds are often identified as ‘Nordic Jackdaws’, but a prominent white crescent is most typical of the race soemmerringii from e. Europe and w. Asia. It may simply be that native British birds occasionally show this feature.
Found only on rocky western coastlines (with some inland in N. Wales). Similar in size to Jackdaw. A stunning bird, easily identified by its red legs and long, decurved red bill; juveniles have orange legs and a shorter orange bill. First-years may be browner on wings and tail. Unlike Jackdaw, the wings are long, broad, square and prominently fingered; the primaries may be noticeably kinked back in certain conditions, most markedly when the adjacent inner primaries are missing or partly grown during the summer moult (Grant 1988). Choughs are absolute masters of the air and are a joy to watch as they glide, twist and swoop over their favoured cliffs, often plummeting earthwards with the wings partially closed and swept back close to the body. Loud and evocative chee-aah calls are very distinctive.
Reference Grant (1988).
