Yet it must be confessed that any attempt to explain 
exactly how birds fly must fail. We can do no more than 
state the more obvious factors which are indispensable to 
flight, and the nature of its mechanism. The subtleties and 
delicate adjustments of actual flight evade us. 
Our appreciation, however, of this supreme mode of 
locomotion will be materially quickened, if we make a point 
of studying the varied forms of flight as opportunities present 
themselves. 
To begin with, it is worth noting that the size of the 
wing decreases with the weight of the body to be lifted—up 
to a certain point, of course. This, perhaps, may seem 
a strange statement to make. But it can be readily verified. 
Compare, for example, the size of the body in relation to the 
wings, in the case of the butterfly and the dragon-fly, on 
the one hand, and the partridge and the crow, on the 
other. The two first named, by comparison, have enormous 
wings. 
Birds, it will be noticed, which haunt woods, or thickets, 
have short, rounded wings, like the wren, the pheasant, or 
the tawny owl. Such, on the other hand, as live in the open, 
like the gull, and the swallow, have long, pointed wings. The 
reason for this is fairly plain. Birds which must steer their 
course through the intricate mazes of a wood, or thicket, 
would find their flight seriously hampered by long wings. 
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