Their nests, being heavy, are not safe on branches up which the strengthening sap no longer rises; and in addition to the nest there is the weight of the sitting-bird, and often that of the other who perches temporarily on the edge. As the branches die they become stiff, and will not bend to the gale this immobility is also dangerous to the nest. So long as the bough yields and sways gently--not much, but still a little--the strong winds do no injury. When the bough becomes rigid, the broad--side or wall of the nest offers an unyielding surface, which is accordingly blown away. The nests which contain young are easily distinguished, despite the height, by the almost continuous cry for food. The labour of feeding the voracious creatures must be immense, and necessity may partly account for the greater boldness of the old birds at that season. By counting the nests from which the cry proceeds the condition of the rookery is ascertained, and the amount of sport it will afford reckoned with some certainty. By noting the nests from which the cry arose last, it is known which trees to avoid in the rook-shooting; for the young do not all come to maturity at the same time, and there are generally a dozen or so which it is best to leave a week or a fortnight later than the rest. When the young birds begin to quit the nests, and are observed perching on the tree or fluttering from branch to branch, they must not be left much longer before shooting, or they will wander and be lost. A very few days will then make all the difference; and so it has often happened that men expecting to make a great bag have been quite disappointed, notwithstanding the evident number of nests; the shooting has been held a day or so too late. The young birds get the use of their wings very quickly, and their instinct rather seems to be to wander than to remain in the immediate vicinity of their birthplace. Some think that the old birds endeavour to entice them away as much as possible, knowing what is coming. It may be doubted if that is the case with respect to the very young birds; but when the young ones are capable of something like extended flight, and can cross a field without much difficulty, I think the parents do attempt to lead them away. When the shooting is in progress, if you will go a little distance from the rookery, out of the excitement of the sport, you may sometimes see two old rooks, one on each side of a young one, cawing to it with all their might. The young bird is, perhaps, on the ground, or on a low hedge, and the old birds are evidently endeavouring to get it to move. Yet they have not learned the only way in which that can be done--i.e. by starting themselves and flying a short distance, and waiting, when the young bird will almost invariably follow.