162 BIRDS AND MAN 



great height, they would descend to the earth again, 



to disappear behind a neighbouring cliff. And on 



each occasion they exhibited that wonderful aerial 



feat, characteristic of the raven, and rare among 



birds, of coming down in a series of long drops with 



closed wings. I am inclined to think that a strong 



wind is necessary for the performance of this feat, 



enabling the bird to fall obliquely, and to arrest the 



fall at any moment by merely throwing out the wings. 



At any rate, it is a fact that I have never seen this 



method of descent used by the bird in calm weather. 



It is totally different to the tumbling down, as if 



wounded, of ravens when two or more are seen toying 



with each other in the air a performance which is 



also practised by rooks and other species of the crow 



family. The tumbling feat is indulged in only when 



the birds are playing, and, as it would appear, solely 



for the fun of the thing ; the feat I am describing 



has a use, as it enables the bird to come down from a 



great height in the air in the shortest time and with 



the least expenditure of force possible. With the 



vertical fall of a bird like the gannet on its prey we 



are not concerned here, but with the descent to earth 



of a bird soaring at a considerable height. Now, 



many birds when rushing rapidly down appear to 



close their wings, but they are never wholly closed ; 



