468 Bird - Lore 



places on the body are naked, with no sign of feather-growth. A careful study 

 of these bare patches in different species of birds has led to a complex and 

 elaborate classification of what are called the feather tracts on the bodies of 

 birds. Not only are feathers, taken separately, found to be of various kinds 

 and complicated structure, but their distribution also is varied and intricate. 

 One must learn first to distinguish the different kinds of feathers, and after- 

 ward the different patterns of their distribution. 



In order to understand better the kinds of feathers and their patterns of 

 arrangement, let us think of a few reasons why it would be inconvenient and 

 far from practicable for a bird to have only one kind of feathers covering the 

 entire body. Without feathers, a bird could probably not fly at all; and with 

 only one kind of feathers, it is doubtful whether it could fly well or perfectly. 

 There are at least four things that feathers must do if they serve the purposes 

 to which they are put. First, they must protect the bird's body by keeping it 

 dry; second, they must further protect the bird's body by assisting in regulating 

 the temperature of the blood ; third, they must act as a special mechanism for 

 flying, and fourth, they must aid in steering the body of the bird in flight. There 

 are various minor uses to which feathers are put, such as bracing the bird 

 against an object, for ornaments, and for cleansing purposes, but their main 

 uses are to protect the body, help regulate the temperature, and assist in flight. 

 For these various purposes, therefore, it is essential that feathers be of differ- 

 ent kinds. 



The fact that they do not grow equally on all parts of the body is only 

 another evidence that every possible saving has been made in reducing the 

 bird's weight and bulk without interfering with its normal activities. 



/I. Covering the body in general, without special adaptation 

 QtTiLL- OR Contour- \ for flight. 



Feathers J 2. In particular places on the bod}-, and specially developed 



\ to aid in flight. 



Down-Feathers 



I:: 



Of adult birds. 

 Of nestlings. 



!i. Semiplumes. 

 2. Filoplumes. 

 3. Powder-down feathers. 



Before defining these different groups, we must next see what a feather is, 

 and learn something of its structure. 



Feathers, like hair, grow out of the skin. If we could look through a micro- 

 scope and see a feather starting to grow, it would seem like a collection of tiny 

 cells pushing out from the skin in somewhat the same manner that a glove 

 finger which has been turned inside may be pushed out. Pushing farther 

 and farther out, these tiny ceUs take a definite course and shape, until they have 



