CHAPTER VII 



COLOURS AND PATTERNS OF YOUNG BIRDS 



The complicated changes in the outer coverings of mammals enable 

 us to understand the still more complicated changes in birds. 

 Primitive mammals appear to have been spotted or striped, marked 

 with patterns that were the expression of the nature of their skin, 

 and of the natural processes of growth. These simple patterns were 

 replaced by patterns of a higher grade, first by a process merely of 

 obliterating them, then by changing them stiU further by the 

 development of counter-shading, of secant and ruptive marks that 

 disguised the natural shape, and of various exuberances of ornamenta- 

 tion. In a very large number of cases the primitive growth patterns 

 are repeated in the young ; sometimes these have disappeared even 

 from the young, which start life in a garb of the second grade, and 

 acquire as they become adult, and especially if they are males, the 

 highest and most specialised kinds of coloration. 



Feathers are even more important to birds than fur is to mammals. 

 Their arrangement, colour and patterns make up the greater part of 

 the appearance that a bird presents to the world, to its friends or to 

 its enemies ; the body of a plucked bird has lost the characteristic 

 size, shape and appearance to an extent that is almost grotesque. 

 The down and contour feathers retain the internal heat of the living 

 body, a necessary protection as the blood of birds is hotter 

 than that of mammals and as their physiological processes are more 

 active. The quills of the wings and tail form the light and strong 

 expanses which are used in flight. A feather is a more elaborate 

 organ than a hair, and there are many kinds of feathers, several 

 kinds of plumage and a very elaborate system of moulting. 



The most characteristic feathers are the large quills which lie in a 

 single row along the outer edge of the joints of each wing and are 

 disposed fanwise on the tail. These are found in all birds ; their 

 quite obvious presence in the flightless ostrich shows that that bird 

 and its allies have lost a power of flight which they once possessed, and 

 they can be identified even in penguins. Brush turkeys are the 



C.A. 97 G 



