50 OUR BIRD ALLIES. 
Nor are its powers of endurance less remarkable, 
for the bird is on the wing, with but little intermission, 
from sunrise until after sunset, its tireless pinions 
appearing as unwearied at the end as at the beginning 
of the day. Excepting during migration, indeed, 
fatigue seems to be a sensation to which the swallow ~ 
is a total stranger, in spite of the exertion necessary 
to sustain its body in the air for so long a period of 
time, and one must perforce marvel at the perfection 
of the muscular system which can achieve such 
results at the expense of so little apparent effort. 
The food of the bird, practically speaking, is 
entirely of an insect character. It has now and again 
been detected in the act of feeding upon sandhoppers 
on the shore, it is true. But such proceedings are 
the exception, and not the rule, for, in the vast 
majority of specimens, insects constitute the whole 
of the diet during the whole of life, and are captured 
in almost incredible numbers. If a swallow be shot 
when on the wing, its crop is certain to be found 
filled to repletion with the bodies of its victims, and 
so tightly is this receptacle sometimes packed that 
the enclosed mass, when released, will at once swell 
out to almost double its dimensions. 
Now, such a mass, large though it may be, forms 
but a small part of the bird’s provisions for the day, 
so that the whole number of insects killed by a single 
swallow during its stay in this country must be almost 
too great to express in figures. Nor is the benefit 
which it thus confers upon us qualified by any 
counterbalancing mischief. Save that it is fond of 
