BIRDS AS DESTROYERS OF INSECTS. 
80 
have much other evidence besides that derived from dissection. 
Direct observation has shown, in many instances, that the 
destruction of wild birds has been followed by a great multi¬ 
plication of noxious insects, and, on the other hand, that these 
latter have been much reduced in numbers by the protection 
and increase of the birds that devour them. Many interesting 
facts of this nature have been collected by professed natural¬ 
ists, but I shall content myself with a few taken from familiar 
and generally accessible sources. The following extract is 
from Michelet, JO Oiseau pp. 169, 170 : 
“ The stingy farmer—an epithet justly and feelingly be¬ 
stowed by Yirgil. Avaricious, blind, indeed, who proscribes 
the birds—those destroyers of insects, those defenders of his 
harvests. Not a grain for the creature which, during the rains 
of winter, hunts the future insect, finds out the nests of the 
numbers appeared, so far as could be judged by watching parent birds of the 
same species, as they brought food to their young, to be much greater than 
that supplied to them when fed in the nest; for the old birds did not return 
with worms or insects oftener than once in ten minutes on an average. If 
we suppose the parents to hunt for food twelve hours in a day, and a nest 
to contain four young, we should have seventy-two worms, or eighteen 
each, as the daily supply of the brood. It is probable enough that some 
of the food collected by the parents may be more nutritious than the earth¬ 
worms, and consequently that a smaller quantity sufficed for the young in 
the nest than when reared under artificial conditions. 
The supply required by growing birds is not the measure of their wants 
after they have arrived at maturity, and it is not by any means certain 
that great muscular exertion always increases the demand for nourish¬ 
ment, either in the lower animals or in man. The members of the English 
Alpine Club are not distinguished for appetites which would make them 
unwelcome guests to Swiss landlords, and I think every man who has had 
the personal charge of field or railway hands, must have observed that 
laborers who spare their strength the least are not the most valiant 
trencher champions. During the period when imprisonment for debt 
was permitted in New England, persons confined in country jails had no 
specific allowance, and they were commonly fed without stint. I have 
often inquired concerning their diet, and been assured by the jailers that 
their prisoners, who were not provided with work or other means of exer¬ 
cise, consumed a considerably larger supply of food than common out-door 
laborers. 
