BIRDS. 
365 
anxious attention, look up into the air to discover 
the cause, and at last perceive a dark point, which 
they can hardly distinguish, floating under the 
clouds. This is a bird of prey, whose distance with- 
draws him from our view, but who cannot escape 
either the vigilance or penetration of the careful 
mother. This occasions her fears, and alarms the 
whole tribe. One of these creatures has been seen 
to continue in this agitation, and her young in a 
manner riveted to the ground, for the space of four 
hours successively, whilst their formidable foe has 
taken his circuits, has whirled about, and hovered 
immediately over their heads. When he at length 
disappears, the mother changes her note, and utters 
another cry that revives all her brood ; and they all 
flock round her with expressions of pleasure, as if 
conscious of their happy escape from danger. 
The body of a bird is neither extremely massive, 
nor equally substantial in all its parts ; but it is well 
disposed for flight, sharp before, and gradually in- 
creasing in bulk till it has acquired its just dimen- 
sions. Such a structure renders it more adapted to 
cut the air, and make itself a passage through that 
element. To qualify it for long flights, in which 
provisions are not always to be obtained ; and to en- 
able it to pass away the tedious winter nights with- 
out eating, nature has supplied it under the throat 
with a bag called the crop, in which it reserves its 
meat. The fluid in which this swims facilitates its 
first digestion. The gizzard, into which only a very 
small quantity of the nourishment enters at a time, 
