20 OUR BIRD ALLIES. 
bird separately, the proportion of insects, &c., to the 
gross amount of its annual food, the character of 
those insects, whether injurious, friendly, or neutral, the 
amount of wild seeds which it destroys, the mischief, 
if any, which it causes by devouring fruit or grain, and 
the good or evil which it may cause in any manner 
peculiar to itself. Then must he balance with the 
utmost care the debtor account against the creditor, 
and finally, by comparing his own conclusions with 
those of others, he must ascertain whether he has 
given due importance, and neither more nor less, to 
every branch of his investigation. And not until 
this has been done by qualified and trustworthy 
observers in all parts of the country can we pretend 
to judge, with any degree of certainty, upon the true 
value of any bird in its relationship to the interests of 
mankind. 
And, even should the final verdict prove adverse, 
a word of warning is necessary with regard to our 
subsequent proceedings. A war between man and 
bird may perhaps be inevitable, but—it must not be 
a war of extermination. No matter how mischievous 
an animal may be, its numbers should never be 
reduced beyond the point at which it ceases to be 
injurious to man; for it must be borne in mind that 
in so doing we cannot but disturb the whole balance 
of Nature, and thus very possibly bring upon our- 
selves a calamity far worse than that which we 
attempted to avert. 
Let us suppose, by way of illustration, that we 
utterly destroy such an insect as the cabbage butter- 
