BIRDS OF NEW YORK STATE 



157 



Bluebird Nu Bm8 



Identify the difl'erent groups of wing feathers and note the 

 spurious wing. The thumb bears a tuft of short feathers, called 

 the spurious wing, that can sometimes be seen along the front 

 margin of the extended wing. 



Killdecr Nu Ke9 



Note how the wing is bent at the wrist and decide in which 

 direction the wing is moving. The joints of the wing have 

 become very firm and strong but there is still considerable flexi- 

 bility to the wrist joint. When the wing is brought upward on 

 the noneffective stroke, this joint is bent and the wing partially 

 folded so that there will be an angle to cut the air. On the 

 downward stroke the wrist joint is held immovable and the wing 

 rigid. 



Black tern Nu TfB6 



Compare with the preceding and determine in which direction 

 the wing is moving. 



Yellowlegs Nu Yd8 



Here the birds are about to alight and the wings are consider- 

 ably arched and probably being held in the one position. Note 

 the position of the legs as a further indication. 



b The legs 



The bird's legs dififer from man's chiefly in that the ankle bones 

 have become fused into one bone, and this greatly elongated to 

 form what is called the tarsus. This is ordinarily the most con- 

 spicuous part of the bird's leg since the thigh bone lies against 

 the body beneath the skin and the shin bone is ordinarily almost 

 concealed by the bird's breast feathers. The muscles of the legs 

 are mostly borne on the thigh bone and thus brought toward 

 the center of gravity. A few muscles are borne on the shin but 

 only tendons are found along the tarsus and toes. The muscles 

 of the legs give the initial spring which lifts the bird into the air. 

 They are then ordinarily folded back under the tail or if very 

 long held straight out behind. In a few birds with rudimentary 

 tails, the feet probably assist in steering and in checking flight. 



American bittern Nu BIAS 



Note the extended legs and identify the various parts. The 

 bird is just springing from the marsh and will later hold its legs 

 straight out behind. 



