464 
ECONOMIC RELATIONS OF OUR BIRDS. 
young beetles of the same species, while, as a matter of fact, the destruction of 
seven very young beetles should be counted a greater service than the destruc¬ 
tion of an equal number of adult forms, since not only is the food required to 
mature the young beetles saved, but the possibility of a deposition of seven 
thousand eggs (it is estimated that one female may lay one thousand eggs), is 
effectually precluded. 
The fragmentary condition, also, of the contents of a bird’s stomach renders 
any purely quantitative system of gauging as fruitful of false values as does the 
inequality of size and weight among insects. A single maxilla, a bit of elytron, 
or a sm all wing would count for almost nothing in the account by such a sys¬ 
tem, while each is positive proof of the d 3 struction of a whole insect of some 
kind, no matter how small the fragment may be. 
But when insects are estimated bulk for bulk with grains, weed seeds and 
fruits, the diversion from true relations reaches the maximum. 
A peck of plums and a peck of curculios, a peck of wheat and a peck of 
chinch-bugs, or a peck of corn and a peck of cut-worms, are manifestly not to 
be considered as equivalent values on opposite sides of any account. 
Even in those cases where the individuals are nearly equal in bulk and weight, 
there is often little justice in offsetting one with the other, for then no account 
/ 
will be taken of the relative service or injury of the two species, or of the dif¬ 
ferent rates of reproduction. 
In view of the fact that we have no standard of insect values, and that, in 
the present state of progress of entomological science, a satisfactory one can 
hardly be furnished, the simplest and, I believe, all things considered, the most 
reliable method of exhibiting the results of observations on the food of birds, as 
well as one which will leave the materials accumulated in the most available 
form for subsequent more critical examination, is to exhibit the number of indi¬ 
vidual forms of life which a bird can be proved to have eaten in as systematic 
a form and as specifically as possible. In the tables which follow under the 
various families of birds, an effort has been made to do this. The second table 
in each case exhibits the details as far as they could be shown in the space 
allowed, and the first table exhibits the same facts brought together under the 
heads “ Elements Beneficial,” ‘‘Elements Deti’imental,” and “ Elements whose 
Economic Relations are Unknown.” There are two general tables introducing 
the body of the report which exhibit the same results for all of the birds 
examined, brought together under the families to which they belong. 
