BIRDS OF KANSAS 11 



The irregularities of the body are filled up and made 

 smooth, so that it offers the least amount of resistance 

 when passing through the air. No matter how great the 

 exertion, there is no perspiration. Perhaps it is because 

 perspiration would cool the body too much by evapora- 

 tion or cause the feathers to mat, and thus seriously in- 

 terfere with flight: 



