128 THE FLIGHT OF BIRDS 



hour together above a cliff that gives the wind an 

 upward incline. There are no fish to be caught 

 there, nor anything material to be got by the per- 

 formance. They are describing spirals high in air, 

 and by their skill they get the wind to relieve them 

 of all hard work. No wonder they enjoy it. To 

 return to the Swallows, whose evolutions are 

 different. When there is a fairly strong breeze 

 blowing, the first thing is with its help to attain some 

 altitude ; they face the wind and it helps to lift 

 them. Then, taking advantage of their position, 

 they enjoy a variety of downward glides. Often they 

 will face the wind and glide downward sideways, their 

 course thus crossing the stream of the wind. If 

 the wind has an upward trend this may be done 

 without loss of elevation, as I hope to show later on. 

 They can, of course, glide downward in the teeth 

 of the wind. Sometimes they will glide sideways 

 in the direction of the wind. In this case there are 

 often two simultaneous movements. The bird glides 

 downward, head leading, across the stream of the 

 wind, but the gale sweeps him along sideways with 

 such velocity that the other movement is obscured. 

 I think this is the explanation of what I saw at 

 Alderney. The birds were practising a sporting 

 manoeuvre ; gaining a little elevation and then 

 letting themselves be carried sideways by the gale. 



Some aerial evolutions that I have just been 

 watching — Swallows and one Swift were the per- 

 formers — included no straight a-head flight before 

 the wind : it was a strong wind, though not a gale. 

 But I do not infer a positive dislike of such a thing. 

 The manoeuvres consist of varieties of tobogganing, 



