BIRDS 



175 



Adaptations for 



Flying. — Flight 

 is the most diffi- 

 cult and energy- 

 consuming meth- 



»x*v 





od of 



moving 



Fig. 320. 

 Cockatoo. 



found among ani- 

 mals, and care- 

 ful adjustment is 

 necessary. For 

 balancing, the 

 heaviest muscles 

 are placed at the 

 lower and central 

 portion of the body. 

 These are the flying 

 muscles, and in some 

 birds (humming birds) 

 they make half of the 

 entire weight. Teeth 

 are the densest of ani- 

 mal structures ; teeth 

 and the strong chew- 

 ing muscles required 

 would make the head 

 heavy and balancing 

 difficult ; hence the chewing apparatus is 

 transferred to the heavy gizzard near the 

 centre of gravity of the body. The bird's 

 neck is long and excels all other necks in 

 flexibility, but it is very slender (although 

 apparently heavy), being inclosed in a 

 loose, feathered skin. A cone is the best 







Fig. 321. — Bird of 

 Paradise (Asia). 



