THE BIRD'S FEATHERS 23 



covered with down, and all is arranged in a system of 

 grouping which, the feathers being rightly placed over 

 one and another, does not in any way interfere with the 

 movements of the body, each movement being in perfect 

 conformity with this feather covering. The feathered 

 areas can be moved independently with the aid of the 

 muscles, and this renders the cleansing of the individual 

 feathers easy and the removing of the fatty substance, 

 which is a matter of great importance. If we watch we 

 see that the bird moves the feathers separately in this 

 cleansing process, drawing them through its beak, and 

 so removing any bits of fat and oily substances that may 

 have collected about the fat glands. 



View of the back of the bird, showing the feather tracts 

 The spaces between the tracts are covered with down. 



