Chapter Fourteen.
The Rookery—Building Nests—Young Birds—Rook-Shooting—Stealing Rooks—Antics in the Air—Mode of Flight—White Rooks.
The city built by the rooks in the elms of the great pasture field (the Warren, near Wick farmhouse) is divided into two main parts; the trees standing in two rows, separated by several hundred yards of sward. But the inhabitants appear to be all more or less related, for they travel amicably in the same flock and pay the usual visit to the trees at the same hour. Some scattered elms form a line of communication between the chief quarters, and each has one or more nests in it. Besides these, the oaks in the hedgerows surrounding the field support a few nests, grouped three or four, in close neighbourhood. In some trees near the distant ash copse there are more nests whose owners probably sprang from the same stock, but were exiled, or migrated, and do not hold much communion with the capital.
In early days men seem to have frequently dug their entrenchments or planted their stockades on the summit of hills. To the rooks their trees are their hills, giving security from enemies. The wooden houses in the two main streets are evidently of greater antiquity than those erected in the outlying settlements. The latter are not large or thick: they are clearly the work of one, or at most two, seasons only; for it is noticeable that when rooks build at a distance from the centre of population they are some time before they finally decide on a site, abandoning one place after another. But the nests forming the principal streets are piled up to a considerable height—fresh twigs being added every year—and are also thick and bulky. The weight of the whole must be a heavy burden to the trees.
Much skill is shown in the selection of the branches upon which the foundations are laid. In the first place, the branch must fork sufficiently to hold the bottom twigs firmly and to give some side-support. Then it must be a branch more or less vertical, or it would swing with the wind too much up and down as well as to and fro. Thirdly, there should be a clear or nearly clear space above the nest to give easy access, and to afford room for it to increase in size annually. For this reason, perhaps, nests are generally placed near the top or outer sides of the tree, where the boughs are smaller, and every upward extension reaches a clearer place. Fourthly, the bough ought not to be too stiff and firm; it should yield a little, and sway easily, though only in a small degree, to the breeze. If too stiff, in strong gales the nest runs the risk of being blown clean out of the tree. Fifthly, no other branch must rub against the one bearing the principal weight of the nest, for that would loosen the twigs in time, and dislocate the entire structure. Finally, rooks like an adjacent bough on which the bird, not actually engaged in incubation can perch and ‘caw’ to his mate, and which is also useful to alight on when bringing food for the young.
It may be that the difficulty of finding trees which afford all these necessary conditions is one reason why rooks who settle at a distance from their city seem long before they can please themselves. The ingenuity exercised in the selection of the bough and in the placing of the twigs is certainly very remarkable. When the wind blows furiously you may see the nest moving gently, riding on the swaying boughs, while one of the birds perches on a branch close by, and goes up and down like a boat on the waves. Except by the concussion of branches beating hard against the nest, it is rarely broken; up to a certain point it would seem as if the older nests are the firmest, perhaps because of their weight. Sometimes one which has been blown down in the winter—when the absence of protecting leaves gives the wind more power on them—retains its general form even after striking against branches in its descent and after collision with the earth.
Elms are their favourite trees for building in. Oak and ash are also used, but where there are sufficient elms they seem generally preferred. These trees, as a rule, grow higher than any others ordinarily found in the fields, and are more frequently seen in groups, rows, or avenues, thus giving the rook facilities for placing a number of nests in close neighbourhood. The height of the elm affords greater safety, and the branches are perhaps better suited for their purpose.
After building in an elm for many years—perhaps ever since the owner can remember—rooks will suddenly desert it. There are the old nests still; but no effort is made to repair them, and no new ones are made. The winds and storms presently loosen the framework, about which no care is now taken, and portions are blown down. Then by-and-by the discovery is made that the tree is rapidly dying. The leaves do not appear, or if they do they wither and turn yellow before Midsummer: gradually the branches decay and fall of their own weight or before the wind.