BIRDS 



159 



N^ 



are called primaries, those on the forearm are the sec- 

 ondaries, those on the upper arm are the tertiaries. Those 

 on the tail are called the tail quills. The feathers at the 

 base of the quills are called the coverts. The thumb bears 

 one or more quills called the spurious quills. Is the wing 

 concave on the lower or upper 

 side ? What advantage is this 

 when the bird is at rest ? When 

 it is flying ? 



Control of Flight. — Did you ever 

 see a bird sitting on a swinging 

 limb ? What was its chief means 

 of balancing itself ? When flying, 

 what does a bird do to direct its 

 course upward ? Downward ? Is 

 the body level when it turns to 

 either side ? Birds with long, 

 pointed wings excel in what respect ? Examples ? Birds 

 with great wing surface excel in what kind of flight ? Ex- 

 amples. Name a common bird with short wings which 

 has a labored, whirring flight. Is its tail large or small ? 

 Does it avoid obstacles and direct its 

 flight well ? Why or why not? When 

 a boat is to be turned to the right, 

 must the rudder be pulled to the right 

 or the left ? (The rudder drags in 

 the water and thus pulls the boat 

 around.) When the bird wishes to 



Fig. 299. — position of go upward, must its tail be turned up 

 Limbs of Pigeon. . . TT . ... 



or down ? How when it wishes to go 



down ? When a buzzard soars for an hour without flapping 



its wings, does it move at a uniform rate ? For what does 



it use the momentum gained when scoing with the wind ? 



Fig. 298. — Plan of Bird. 



s, center of gravity. 



