94 THE FLIGHT OF BIRDS 



curve begins. Further out the whole breadth of 

 wing is curved ; for some distance from the front 

 margin there is an upward slope, then a downward 

 slope sets in. In the nearer region, also, there is not 

 a simple curve maintained throughout, but the 

 feathers in one part are more bent down than in 

 another, so that the back edge presents a curiously 

 undulating line. The Sparrow-Hawk's wing has 

 similar curves, but they are much less pronounced. 

 What the exact significance of all this complication 

 may be, presenting so marked a contrast to the 

 uniform curves of an aeroplane, it is difficult to say. 

 Probably there is some significance, since in birds 

 that are strong on the wing the whole mechanism 

 of flight down to minute details is so efficient. 



Sometimes we may see the wing-curves in their 

 full beauty in a live bird, but it is only for a moment, 

 and one wishes to look at them quietly and study 

 them. The thing is, if one has a freshly-killed 

 specimen, to cut off the wings close to the body and 

 pin them out back downwards at their full stretch. 

 Treated thus the wing retains its curves and a great 

 deal of its beauty. If it is pinned face downwards 

 and flattened, it conveys by no means so good an 

 idea of what it was during the life of the bird. I 

 have tried by photographs to show the outlines of 

 various types of wing, the depth of their concavities, 

 and the undulating curves seen in, for instance, the 

 Curlew's wings. Some points come out distinctly, 

 others the camera fails to see or does not see clearly. 



To show the gradual tapering and flattening of 

 the farther half, perhaps no wings are better than 

 those of the Gannet and the Tern (PI. xiv), and 



