The commonest form of play in birds is flying play. Any one who has kept his eyes open at the seaside will have seen the Herring Gulls congregate in soaring intersecting spirals where the cliff sends the wind upwards. But such flights are nothing compared with those of other birds. Even the staid black-coated Raven may sometimes be seen to go through a curious performance. One I remember, all alone, flying along the side of a mountain near Oban; but instead of progressing in the conventional way, he flew diagonally upwards for a short distance, then giving a special croak with something of gusto in it, turned almost completely over on to his back, and descended a corresponding diagonal in this position. Then with a strong flap of the wings he righted himself, and so continued until he disappeared round the shoulder of the hill half a mile on. It reminded me of a child who has learnt some new little trick of step or dance-rhythm, and tries it out happily all the way home along the road. Mr. Harold Massingham has seen the Ravens’ games too, and set them down more vividly than I can.[26] He also is clear that they play for the love of playing, and even believes that their love of sport has helped their downfall to rarity by rendering them too easy targets for the gunner. Or again, at the Egret rookery in Louisiana, at evening when the birds returned in great numbers, they came back with steady wing-beats along an aerial stratum about two hundred feet up. Arrived over their nesting pond, they simply let themselves drop. Their plumes flew up behind like a comet’s tail; they screamed aloud with excitement; and, not far above the level of the trees, spread the wings so that they caught the air again, and as result skidded and side-slipped in the wildest and most exciting-looking curves before recovering themselves with a brief upward glide and settling carefully on the branches. This certainly had no significance for courtship; and I never saw it done save over the pond at the birds’ return. It seemed to be simply an entertaining bit of sport grafted on to the dull necessity of descending a couple of hundred feet. Examples could be multiplied: Rooks and Crows, our solemn English Heron, Curlew, Swifts, Snipe--these and many others have their own peculiar flying sports. What is clear to the watcher is the emotional basis of these sports--a joy in controlled performance, and excitement in rapidity of motion, in all essentials like the pleasure to us of a well-hit ball at golf, or the thrill of a rapid descent on sledge skis. For any one to whom the evolution theory is one of the master-keys to animate nature, there must be an unusual interest in tracing out the development of lines of life that, like the birds’, have diverged comparatively early from the line which eventually and through many vicissitudes led to Man.