Unlike its cousin the jackdaw, which commonly nests in the cliffs, the rook is not, perhaps, commonly associated with the immediate neighbourhood of the sea, but a colony close to my own home in Devonshire displays sufficiently interesting adaptation to estuarine conditions to be worth passing mention. Just in the same way that gulls make free of the wireworms on windswept ploughlands, so in early summer do the old rooks come sweeping down from the elms on the hill that overlooks my fishing ground and take their share of cockles and other muddy fare in the bank uncovered by the falling tide. Here, in company with gulls, turnstones, and other fowl of the foreshore, the rooks strut importantly up and down, digging their powerful bills deep in the ooze and occasionally[47] bullying weaker neighbours out of their hard-earned spoils. The rook is a villain, yet there is something irresistible in the effrontery with which one will hop sidelong on a gorging gull, which beats a hasty retreat before its sable rival, leaving some half-prized shellfish to be swallowed at sight or carried to the greedy little beaks in the tree-tops. While rooks are far more sociable than crows, the two are often seen in company, not always on the best of terms, but usually in a condition suggestive of armed neutrality. An occasional crow visits my estuary at low tide, but, though the bird would be a match for any single rook, I never saw any fighting between them. Possibly the crow feels its loneliness and realises that in case of trouble none of its brothers are there to see fair play. Yet carrion crows, like herons, are among the rook's most determined enemies, and cases of rookeries being destroyed by both birds are on record. On the other hand, though the heron is the far more powerful bird of the two, heronries have likewise been scattered, and their trees appropriated, by rooks, probably in overwhelming numbers. Of the two the[48] heron is, particularly in the vicinity of a preserved trout stream, the more costly neighbour. Indeed it is the only other bird which nests in colonies of such extent, but there is this marked difference between herons and rooks, that the former are sociable only in the colony. When away on its own business, the heron is among the most solitary of birds, having no doubt, like many other fishermen, learnt the advantage of its own company.
One of the most remarkable habits in the rook is that of visiting the old nests in mid-winter. Now and again, it is true, a case of actually nesting at that season has been noticed, but the fancy for sporting round the deserted nests is something quite different from this. I have watched the birds at the nests on short winter days year after year, but never yet saw any confirmation of the widely accepted view that their object is the putting in order of their battered homes for the next season. It seems a likely reason, but in that case the birds would surely be seen carrying twigs for the purpose, and I never saw them do so before January. What other attraction the empty nurseries can[49] have for them is a mystery, unless indeed they are sentimental enough to like revisiting old scenes and cawing over old memories.
The proximity of a rookery does not affect all people alike. Some who, ordinarily dwelling in cities, suffer from lack of bird neighbours, would regard the deliberate destruction of a rookery as an act of vandalism. A few, as a matter of fact, actually set about establishing such a colony where none previously existed, an ambition that may generally be accomplished without extreme difficulty. All that is needed is to transplant a nest or two of young rooks and lodge them in suitable trees. The parent birds usually follow, rear the broods, and forthwith found a settlement for future generations to return to. Even artificial nests, with suitable supplies of food, have succeeded, and it seems that the rook is nowhere a very difficult neighbour to attract and establish.
Why are rooks more sociable than ravens, and what do they gain from such communalism? These are favourite questions with persons informed with an intelligent passion for acquiring information, and the best[50] answer, without any thought of irreverence, is "God knows!" It is most certain that we, at any rate, do not. So far from explaining how it was that rooks came to build their nests in company, we cannot even guess how the majority of birds came to build nests at all, instead of remaining satisfied with the simpler plan of laying their eggs in the ground that is still good enough for the petrels, penguins, kingfishers, and many other kinds. Protection of the eggs from rain, frost, and natural enemies suggests itself as the object of the nest, but the last only would to some extent be furthered by the gregarious habit, and even so we have no clue as to why it should be any more necessary for rooks than for crows. To quote, as some writers do, the numerical superiority of rooks over ravens as evidence of the benefits of communal nesting is to ignore the long hostility of shepherds towards the latter birds on which centuries of persecution have told irreparably. Rooks, on the other hand, though also regarded in some parts of these islands as suspects, have never been harassed to the same extent; and if anything in the nature[51] of general warfare were to be inaugurated against them, the gregarious habit, so far from being a protection, would speedily and disastrously facilitate their extermination. Another curious habit noticed in these birds is that of flying on fine evenings to a considerable height and then swooping suddenly to earth, often on their backs. These antics, comparable to the drumming of snipe and roding of woodcock, are probably to be explained on the same basis of sexual emotion.
The so-called parliament of the rooks probably owes much of its detail to the florid imagination of enthusiasts, always ready to exaggerate the wonders of Nature; but it also seems to have some existence in fact, and privileged observers have actually described the trial and punishment of individuals that have broken the laws of the commune. I never saw this procedure among rooks, but once watched something very similar among the famous dogs of Constantinople, which no longer exist.
The most important problem however in connection with the rook is the precise extent to which the bird is the farmer's enemy or his friend. On the solution hangs the rook's fate[52] in an increasingly practical age, which may at any moment put sentiment on one side and decree for it the fate that is already overtaking its big cousin the raven. Scotch farmers have long turned their thumbs down and regarded rooks as food for the gun, but in South Britain the bird's apologists have hitherto been able to hold their own and avert catastrophe from their favourite. The evidence is conflicting. On the one hand, it seems undeniable that the rook eats grain and potato shoots. It also snaps young twigs off the trees and may, like the jay and magpie, destroy the eggs of game birds. On the other hand, particularly during the weeks when it is feeding its nestlings, it admittedly devours quantities of wireworms, leathergrubs, and weevils, as well as of couch grass and other noxious weeds, while some of its favourite dainties, such as thistles, walnuts, and acorns, will hardly be grudged at any time. It is not an easy matter to decide; and, if the rook is to be spared, economy must be tempered with sentiment, in which case the evidence will perhaps be found to justify a verdict of guilty, with a strong recommendation to mercy.