16 



THE BIRDS 



constructed primarily for flight, they are provided with a light 

 skeleton, combined with very powerful muscles. The skele- 

 ton is very compact, and contains a relatively small number 

 of bones (Fig. 7). The neck is long, and quite movable. 

 The most characteristic external features of the bird are 

 the fluffy feathers which cover the whole body, the well 

 developed wings, and clearly defined tail. The wings propel 

 the birds when in flight, and the tail is used to steer them in 

 flight. The mouth of the bird is guarded by a beak in the 

 case of land birds, and by a bill in the case of water birds. The 



Second joint 

 of winy 



First joint 

 of wing 



outer joint of wing 



Sack of skull 



Tialfofb&Lk 



Backbone 

 firstjbwtoftey 



S203 



Ifecfc Zones 

 Wz\sh bone or clavicle 



Second joint o?2eg, 

 often catted 

 drum stick 



Shank or low&rjoint 

 ofleg ' 



FIG. 7. The skeleton is made up of small bones which are covered with powerful 

 muscles, giving strength and lightness. 



nostrils are located just above the base of the beak. The 

 ears lie just below the back of the eye, and are covered by 

 a protective growth of feathers. The breast of the bird is 

 rather sharp and pointed, acting as a cutter with which to 

 cleave the air when the bird is in flight. The legs are usually 

 short and thick, except in the heron and other marsh birds, 

 in which case they are very long and slender. The feet usually 

 have four toes; in land and aerial birds they are round, 

 gently curved, and fitted with claws. Aquatic birds have a 

 thick web or membrane between the toes, which assists 



