296 



The Bird 



forms entirel}' different, and thought to be due solely 

 to the amount of moisture in the ground on which it lives. 

 Very dark-coloured and ver\- pale individuals live within 

 a few hundred }-ards of each other, in dry and swamp}* 

 situations respectixely, each, it is said, keeping entirel}' 

 to its own little beat. 

 .- We are all fan;iliar with the changes of colour due to 





iigr'^^^v;^/'^ 



Fig. 2:i(i. — i\'ightha\vk perching Iciigtlnvise oi) a fallen liraneh. 



age, as, for instance, in the young Rose-breasted Gros- 

 beaks, which are very different from the male parent, and 

 the young Bald Eagles, which lack the white colour of the 

 feathers of head and tail. Certain wild pigeons show 

 marked differences in colour patterns between the young 

 birds and the a(hilts, and very good evidence of the gradual 

 evolution which must liavo ])receded these changes is 



