INTRODUCTION OF BIRDS. 115 
An unfortunate popular error greatly magnifies the injury 
done to the crops of grain and leguminous vegetables by wild 
birds. Very many of those generally supposed to consume 
large quantities of the seeds of cultivated plants really feed 
almost exclusively upon insects, and frequent the wheatfields, 
not for the sake of the grain, but for the eggs, larvae, and fly 
of the multiplied tribes of insect life which are so destructive 
to the harvests. This fact has been so well established by the. 
examination of the stomachs of great numbers of birds in 
Europe and the United States, at different seasons of the year, 
that it is no longer open to doubt, and it appears highly prob- 
able that even the species which consume more or less grain 
generally make amends by destroying insects whose ravages 
would have been still more injurious.* On this subject, we 
* Even the common crow has found apologists, and it has been asserted that 
he pays for the Indian corn he consumes by destroying the worms and larvee 
which infest that plant. 
Professor Treadwell, of Massachusetts, found that a half-grown American 
robin in confinement ate in one day sixty-eight worms, weighing together 
nearly once anda half as much as the bird himself, and another had pre- 
viously starved upon a daily allowance of eight or ten worms, or about twenty 
per cent. of his own weight. The largest of these 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 earthworms, and consequently that a smaller quantity suf- 
ficed 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 nourishment, either 
in the lower animals or inman. 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, per- 
sons confined in country jails had no specific allowance, and they were com- 
