ADAPTATION IN BIRD ANATOMY 



Adaptation is a principle that runs 

 through all nature. There is no fact 

 more prominent. It is .nature's response 

 to demand, her answer to necessity. 

 The large muscle of the blacksmith ; 

 the calloused hand of the laborer and the 

 coiled tendrils of the vine, are very fa 

 miliar examples. But nowhere is the 

 principle more conspicuous than in 

 bird anatomy. Birds are so sensitively 

 organized, and respond so readily to en 

 vironment, that the finest shades of 

 adaptation are exhibited. It is the pur 

 pose of this article to point out some of 

 the most important examples' of adapta 

 tion to be found in birds, and to show 

 how a knowledge of these facts may 

 help us to interpret bird life. 



In the first place; birds fly, and hence 

 have wings. Though some may choose 

 to contend that they have wings and 

 hence fly. However that may be, wings 

 alone are not sufficient for flight. A 

 little examination reveals the fact that 

 the bones of birds are hollow through 

 which warm air circulates, evidently to 

 give the bird buoyancy* and render 

 flight more easy. An exception which 

 is additional proof of the principle of 

 adaptation is the more solid bones of the 

 ostrich and domestic fowls, which do not 

 fly. Furthermore, it is found that the 

 feathers stand out on the body of the 

 bird in such a way as to displace con 

 siderable air, which to no small degree 

 enhances the bird's power of flight. By 

 removing the feathers from the body of 

 the bird, leaving the wings entire, flight 

 becomes very awkward and difficult, and 

 in some cases is practically destroyed. 



The keel-like form of the body is es 

 pecially adapted for flight, and the large 

 wing muscles of the breast account for 

 the untiring ease with which some exer 

 cise this power. Birds with remarkable 

 power of flight have these wing muscles 

 very highly developed ; while in birds 

 like the grebe, which fly but little these 

 muscles are almost wanting ; but being 



lusty swimmers they have large leg 

 muscles instead. 



Turning to other parts of the bird an 

 abundance of material for our subject 

 will be found. Just as we are enabled to 

 read on the face of an individual quite 

 accurately the story of his inner life, so 

 is there expressed if we will but read 

 in the modifications of the several parts 

 of the bird, his habits, character and 

 environment. If his birdship would 

 conceal these secrets it is always neces 

 sary that he hide his head and feet, 

 and even then his leg, or wing, or tail, 

 may tell it all. 



The feet of those birds that spend 

 much of their time on the ground (the 

 Robin, Lark, and domestic fowls for ex 

 ample) are very large, obviously for the 

 reason that they are much used. On 

 the other hand, the feet of the Chimney 

 Swift, which are practically never used, 

 for these birds do not perch except on 

 the nest, are very small in fact all but 

 wanting. The Night-hawk, whose habits 

 are very similar, has legs to small to 

 support the body, so instead of perching 

 crosswise of the limb as most birds do, 

 rests the body on the limb parellel to it. 

 This brings to our mind that oft re 

 peated law of nature: "If you do not use 

 you lose," which, however, is merely 

 an expression of one side of this princi 

 ple of adaptation. 



It will be observed that those birds 

 that perch a great deal have well de 

 veloped claws, while the Kildeer, a bird 

 that never perches, has no claws at all 

 to speak of. The same is wanting in 

 Grebes and other water birds. Birds of 

 prey have strong, sharp claws ; the rea 

 son is very evident. 



The number, position, and relative 

 size of the toes of birds is a very large 

 and interesting study in itself. As a 

 rule birds have four toes, three of which 

 point forward, the other backward 

 all on a level. But there are many Vari 

 ations from this rule. The hind toe of 



