BIRDS AND BIRD LIFE 17 



them to swim. The wings consist of three distinct parts, 

 the inner portion being a part of the body proper, and the 

 other two portions being outside of the body. The wings 

 correspond to the forearm of man. When not used for 

 flight they are usually folded close to the body. On the 

 extremity of the wings are the flight feathers, commonly 

 called the primaries. To the next joint of the wing are 

 attached the secondary flight feathers. When the wing is 

 folded, the secondaries are visible, the primaries being con- 

 cealed under them. In full flight these heavy wing feathers 

 are widely spread, and form the propelling power. 



Feathers. — The feathers on the body of a bird are an 

 outgrowth from the skin. They consist of an elongated 

 hollow quill, and a lateral or side growth, called a vein or 

 web (Fig. 8). The lower part of the quill is rather heavy 

 and is filled with a pithy material; this portion is often 

 called the staff. Each individual hair which makes the web 

 is called a barb. On the end of the small barbs are little 

 hooks, or curved hairs, which serve to hold the barbs 

 together. These barbs or small hooks can be detected only 

 by a magnifying glass. Barbed feathers which have no 

 hooks are called down. Feathers do not cover the entire 

 body of the bird, but are found in certain areas or tracts, 

 being separated from each other by featherless spaces. 

 When the bird has its full plumage, these tracts are not 

 apparent, as the feathers grow in such a way as entirely to 

 conceal the spaces. 



Plumage color varies greatly in different species, that 

 of the male bird being usually more vivid and brilliant than 

 that of the female. Once, and sometimes twice, a year the 

 birds change their plumage; in our domestic breeds this is 

 called the molt. In some birds this change of feathers is quick, 

 in others slow and gradual. With domestic birds a complete 

 molt is made during the month of August. With wild birds 

 it usually occurs after the mating season. 



