408 The Bird 
in flight depends but little upon the shape of the tip, 
when we consider certain birds with cuneate tails, or 
those in which 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 Mexican 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 
Fic. 323.—Tail of Grass Parrakeet. 
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. 
