Among the larger birds the rule is for each species to keep to itself. Even when several kinds may be feeding on the same ground, each quietly shakes itself free from the others when they are disturbed, and all go off in their separate bands. An exception to this is the frequent mixing of rooks and jackdaws, or rather of jackdaws with rooks.
Rooks, jackdaws and crows may be seen together on the same field or marsh. These birds are with us all the year round, but it is one thing to know them at their nesting places and quite another to recognise them in their winter quarters. According to the reference books the rook has a white patch of bare skin at the base of the beak and the crow has not, and the jackdaw is smaller than the other two and has grey on the back of his head and neck. Unfortunately these rules are not always enough to enable you to identify the birds in the open air. If you see a black bird that is large enough to be a member of the crow family and can be sure that it has the white bare skin at the base of the beak, you may be satisfied that it is a rook. But sometimes the light is deceptive, especially when the bird is at a distance, and causes you to think you see a white mark where there is none, and so you may believe a bird to be a rook though it is really a crow. Besides, not all rooks have the white patch, as I have shown in Chapter Eleven. So you may often see birds that seem to be crows though they are really rooks.
The rook's beak is straighter and more slender than the crow's. When he is on the ground some of the rook's feathers hang down round the upper part of his legs in such a way as to suggest that he is wearing knickerbockers or shorts. The crow's feathers all fit close to its body.
A readier means of distinguishing the two is that the rook flies and feeds in flocks and the crow singly or in pairs. But even this is not always to be depended upon; for often you may see a solitary rook flying overhead or sitting on a tree or searching for food, and it is not uncommon in autumn and winter for crows to live in parties.
The rook alights on the ground and walks about in a stately manner, picking up tit-bits here and there as he goes. His food consists of little things, such as worms, grubs and corn. But the crow is the carrion crow, and his favourite meal is the flesh of some dead animal, so he flies about in search of some such prize and alights when he finds it. Still, while he is in flight he may easily be mistaken for a rook, and the rook sometimes eats carrion.
Once you know the calls of the rook and the crow you need never confuse the two birds. Most people are unable to distinguish these calls because they are not in the habit of noticing the sounds they hear, and their attention has not been drawn to the difference. The rook's is a deep, hoarse ca-a-aw, and the crow's is a harsh car-r-r. The crow usually sounds his three times in quick succession, thus carr-carr-carr.
Unfortunately the carrion crow's call is the same as the hooded crow's. So when you hear it, though you need never mistake it for the call of the rook, you cannot be certain that it has been uttered by a carrion crow without actually seeing the bird. If you do see it and get a clear view of it, you will have no difficulty in deciding whether it is a hooded crow or not, for this bird has a slate grey body and black head, wings and tail.
Another species that may be mistaken for the carrion crow is the raven. This is a larger bird and has a much heavier bill. But at a distance you cannot depend on size as a guide, and in that case the only sure test is the call note. The raven's call is quite distinctive. It is a deep cr-r-ruck, which is uttered repeatedly. The raven lives in mountainous districts and on the coast, where there are inaccessible rocky cliffs on which it can roost and rear its family in security. It is in such districts only, therefore, that you are likely to confuse the raven with the crow. In other parts of the country the raven may be ruled out when you have any difficulty in identifying a member of the crow family.
Everywhere, however, the jackdaw is extremely common, and in flight he may be easily mistaken for either the crow or the rook. He is the smallest of the tribe, but, of course, at a distance the smallness of the jackdaw is no better guide than the largeness of the raven. His wingbeats are quicker than those of his larger cousins, and they are one of the signs by which you may know him when you are familiar with the bird and have been able to compare his flight frequently with that of the rook. At close quarters the jackdaw may be recognised by the grey patch on the back of his head. But his call is characteristic, and he will never keep you waiting long for that. He is constantly repeating his own name, Jack, as if he liked the sound of it. It is shorter and sharper than the call of the rook, and for comparison may best be represented by the syllable kya. But like most birds, the jackdaw has several calls, and one of them is not unlike the caw of the rook.
Jackdaws Nest Building
From plate pp111 by C.F. Tunnicliffe
There is one more black member of the crow tribe, the chough, but it is rare. The magpie and the jay also belong to this interesting family, but as each of them has a very striking plumage of its own, it is not possible to confuse them with any of their relatives. The magpie's black and white coat and his long black tail are unmistakable. His call is just as unmistakable, once you know it. It is a loud chattering cry, like chac-chac- chac-chac-chac-chack repeated rapidly. Naturally the magpie flocks in winter, and at one time parties numbering as many as twenty were to be seen in field and wood. Then the gamekeepers persecuted the species till it was reduced to isolated pairs. But during the Great War it was relieved from their attentions and was able to multiply. It is now fairly plentiful. I have myself had the pleasure of seeing six of these handsome birds on one thorn bush.
The jay is such a wary, shy bird that it is difficult to see him at close quarters. At the first sign of your approach, he flies off to a safe distance, uttering as he goes the harsh screaming note that has given him his name; it sounds like the tearing of a piece of cotton. It is seldom that you can get near enough to a jay to see the beautiful blue patch on his wings. But his reddish brown back with a large white patch on the rump and his black tail are conspicuous as he flies away from you. His manner of flight is also characteristic. It suggests that he is feeble, and when you see him crossing an open space you find yourself wondering whether he will be able to reach the farther side. This bird does not flock in summer, but it lives all the year round in colonies, and at pairing time the members of such communities hold some noisy meetings in the tree-tops
From plate pp285 by C.F. Tunnicliffe