AN ESSAY ON BIRD-MIND 129 



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 neces- 

 sity 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 emo- 

 tional basis of these sports — a joy in controlled per- 

 formance, 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. 



In the birds as in the mammals, and quite sepa- 

 rately in the two groups, we see the evolution not only 

 of certain structural characters such as division of 

 heart, compactness of skeleton, increase of brain-size, 

 not only of physiological characters like warm- 



