128 THE FLIGHT OF BIRDS 
hour together above a cliff that gives the wind an 
upward incline. The 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 avariety 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 
manceuvre; 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 manceuvres consist of varieties of tobogganing, 
™s 
