The Audubon Societies C3 



kinds of birds only to find that they are so much aUke that it seems improbable 

 that they were ever meant to serve any other purpose than that of flight. An 

 exception may be made in the case of the Penguin, whose wing-bones which arc 

 coxered with tiny feathers that resemble somewhat scales, serve as oar- 

 blades. The Penguin is a fine swimmer, but is awkward on land and 

 practically flightless in air. There are some birds of an ancient type, 

 like Ostriches, Cassowaries, Kiwis, etc., which are called flightless; but an 

 examination of their wing-bones shows that, although these bones are small 

 as compared with the size and weight of the birds to which they belong, they 

 are nevertheless made on the true flying plan. Ages ago the ancestors of these 

 birds doubtless were good fliers. We may think of the wings of a bird, then, as 

 its most important flying apparatus. By means of the rigid breast-bone, to 

 which the huge muscles of flight are attached, the bird attains great stability 

 in the air, but, in order that it can really fly, its wings must also be flexible. 

 Examine the wing of a roasting-chicken and see how easily the different joints 

 move in one direction. It is a curious fact that even so small a part of the 

 "wishbone" of modern birds as the tip end is very important in connection 

 with flight. In fact, if it becomes broken, the bird loses control of the flight 

 muscles and becomes unable to fly. 



Flight is so much more complicated than walking or crawling or running 

 that we cannot expect to understand it until we have studied the subject a 

 long time, even then, it is doubtful whether anyone could entirely explain it. 

 We can, however, notice that a bird does different things with its wings, such 

 as fluttering, hovering, skimming, and soaring, which are all different motions 

 from plain flying. We can observe, also, which birds are able to soar and 

 hover and which are not. 



Wings alone cannot make perfect flying. Lightness, one of the usual 

 accompaniments of good flight, is attained by a very pecuHar pneumatic 

 device — that is, hollow bones filled with air together with a system of air- 

 sacs connected with the lungs. Still, not all flying birds have hollow bones. 

 Such fine fliers as the Gulls, for example, lack this pneumatic equipment. 

 Equilibrium is an essential to successful flight, and in birds this seems to be 

 correlated with the steering-apparatus. Watch birds in flight and see whether 

 you notice any device like a rudder. The motions of birds in flight are so 

 numerous and complex that one rudder alone would scarcely serve to insure 

 perfect equilibrium. By studying these movements closely it seems evident 

 that the tail and the head and neck together, as well as certain wing-motions 

 aid the bird both in steering its course and at the same time keeping its 

 equilibrium. As we shall see later, the feet are useful in some species as 

 rudders. 



Moulting birds are often quite helpless for a time about governing their 

 flight, or even flying at all. The tail, as we see it, is mostly made up of large 

 feathers, and these feathers we soon find are of much importance in aiding 



