i66 



The Bird 



is attested by their distinctness in our ears after the bird 

 has passed beyond the range of vision. A human singer 

 is compelled to put forth all his energy in his vocal ef- 

 forts, and if, while singing, he should start on a run even 

 on level ground, he would become exhausted at once. 

 The apparatus which gives to a duck the ''wind" to out- 

 strip an express train, and to a Mockingbird notes which 

 hold us spellbound as by a moti] of grand opera, is most 

 interesting, and as easy to understand in its general scheme 

 as it is effective in operation. 



The Trachea, or Windpipe 



Look into the beak of a sparrow or pigeon and directly 

 back of the tongue, on the floor of 

 the mouth, a narrow slit is visible 

 — the glottis, or opening of the 

 windpipe. In the gaping yellow 

 mouth of a nestling robin this 

 may be seen to excellent advan- 

 tage, and watched as it widens and 

 narrows with each breath. But 

 give the young bird a mouthful 

 of food, and this air-passage closes 

 instantly and remains so until all 

 danger of an intruding substance 

 is past. No matter how suddenly 

 you may eject a stream of water 

 from a medicine-dropper into the' 

 bird's mouth, reflex action will 

 anticipate the danger of choking and close the aperture. 



Fig. 120— Open glottis of 

 a Pelican. 



