STARTING 57 



of proved fact. Even now, though the subject has 

 been much studied, it would be very rash to venture 

 on a formula. The big bird has great advantages. 

 He can manage, as we have seen, with a relatively 

 smaller expanse of wing, for the area, being greater 

 absolutely, does not so readily allow the escape of 

 air at the margins. Moreover, his wing, being longer 

 absolutely, is a more powerful lever. The great 

 weights which Eagles, for example, carry show that 

 there is no deficiency of lifting power. But the big 

 bird's wings have not the easiness of rotation at the 

 shoulder- joint which makes it possible for a Green- 

 finch, for instance, or a Pheasant, to rise with a steep 

 incline ; he cannot put himself in the right attitude. 

 It does not appear, however, that bulk in itself is 

 any handicap. 



If this be so, it may well be asked why even big 

 birds are quite small when compared with the larger 

 mammals. I have already pointed out that the big 

 bird, if his legs are short, has difficulty in beginning 

 a flight, and so lacks a very important accomplish- 

 ment. Then why are they not all mounted on stilts, 

 like the Flamingo ? But legs of such length, or even 

 the half of it, would for many birds be most incon- 

 venient appendages, for a diving bird most of all. 

 They would not help him to rise from the water, and 

 they would be clumsy things beneath the surface. 

 And thus among big birds there are many that for 

 purposes of flight are handicapped by shortness 

 of leg. Diminutive size brings with it another 

 advantage. The small bird comes more rapidly to 

 maturity. In his second spring, when he is not yet 

 twelve months old, the Blackbird has already paired 



