262 THE STRUCTURE AND LIFE OF BIRDS chap. 



and we should expect that unless some new factor 

 should come in and upset the calculation, the areas 

 would vary as the weight of the winged animal, 

 whether bird or insect. That this is not the rule is 

 shown by the following examples. 1 



Wing area per kilogram. 



Dragon-fly ... 44,032 sq. inches. 



Swallow 1 ? 5442 51 



Vulture 260 „ 



Australian Crane 139 ,, 



Thus the Australian Crane has in proportion to its 

 weight only a little more than half the wing area of a 

 Vulture, rather less than Jy of that of the Swallow 

 and not quite ^ F of that of a Dragon-fly ! 2 



How are we to account for these facts ? Before 



1 These figures are those of M. de Lucy, quoted by Professor 

 Pettigrew, Animal Locomotion ; also by Professor Marey, 

 Animal Mechanism, p. 222. I have not referred to M. de 

 Lucy's work, but the quotations agree. 



2 The following figures from L. P. Mouillard's U Empire de 

 I air are interesting. They give in grammes the weight sup- 

 ported by one square metre of surface, the whole undersurface of 

 the body as well as that of the wings being included. The 

 small birds, as a rule, have far more surface for their weight, 

 though the cock Kestrel heads the list and is an exception 

 difficult to account for. Most startling is the small amount of 

 surface that the Goose, Turkey, and Duck have to support 

 them. 



