The art and science of "shifting" is indeed one of the most elaborate that is possessed by the dumb creature. Almost all birds cultivate it to a certain degree. Instinct suggests it to them; but many birds improve upon their natural powers by frequent practice. Who has not seen one rook chasing another, either in sport or in a petulant humour, and the fugitive evidently enjoying the fun of throwing out his persecutor? In the tropics there is nothing that a crow likes better than stooping at kites; and nothing that the kite takes greater pride in than showing how easily he can elude the shots so made at him. I have seen pigeons, when a slow or lazy peregrine is in the air, deliberately hang about within reach of her for the express purpose of enjoying the amusement of successfully shifting when she makes a dash for them. Indeed, it will be seen in Chapter XIX. that I saw this game played rather too rashly by a house-pigeon with a trained ger-tiercel. It has been said that the rook in full plumage is no mean flier. He has also a good head on his glossy shoulders, and he shifts cleverly enough while his lungs and muscles hold out. He does not often lose his head, in the metaphysical sense. Sometimes, when particularly close shots graze him, or even feather him, he is frightened into wasting a little breath in an angry complaining croak. But this is almost the only piece of stupidity that can be alleged against him. Usually, however hard pressed, he keeps all his wits about him; and when he is beaten in the air, it is oftenest from sheer want of speed and want of wind. The violent effort required to escape by shifting a good stoop of a first-rate peregrine takes it out of him terribly. The whiz of the falcon as she rushes by is enough to make the stoutest heart quail. But cowardice is not the weak point of the rook, who, for the most part, has a determined and fair struggle for his life.