40 



8 



The Bird 



in flight depends but Httle upon the shape of the tip, 

 when we consider certain birds with cuneate tails, or 

 those in wliich the central feathers, soft and not rigid, 

 are elongated, instead of the outer ones. 



The Undulated Grass Parrakeet shows a condition 

 almost the opposite of the swallow. The iMexican long- 

 tailed jays, the magpies, and the tropic-birds are also 

 all of this type, the latter being especially fine fliers and 

 capable of remarkable aerial evolutions. Again, some 



Fig. 323. — Tail of Grass Pariakeet. 



of the flycatchers with moderate, rounded tails can exe- 

 cute most wonderful flight movements, steering in erratic 

 darts through the air, or darting aside at right angles 

 while at full speed, this being accomplished principally 

 by means of the tail. 



A tail serves also an important use as a brake. When 

 a great pelican settles gradually toward the surface of 

 the water, or a duck momentarily hovers before alighting, 

 the tail, wide-spread and brought downward, gives effi- 

 cient aid in retarding the impetus. 



