110 
The Food of Birds. 
mary of the food of the robin as a species in at least the 
northern half of the State, and under the ordinary condi- 
tions of the last five or six years. Of course, I had no - 
idea how these averages were coming out until my notes 
were finished and the ratios were calculated for the whole. 
Economic Relations. 
We come now to the intricate, delicate and difficult 
question of the economic relations of this species — a 
question rendered less important by the general consid- 
erations urged elsewhere, but, nevertheless, deserving 
careful attention. While it is true that every insectivo- 
rous bird must be respected, whatever its other habits, at 
least until we clearly understand its function in the gen- 
eral order and are certain that its removal will do no 
harm which we cannot remedy or endure better than we 
can support its injuries, yet an idea of the relative im- 
portance of edible fruits and insects of both the benefi- 
cial and injurious classes in the diet of the bird is neces- 
sary as a step to this clear and complete understanding 
of the matter. 
Glancing at the bottom of the table of the food of the 
species on page 115, the reader will see three lines of fig- 
ures running across the page, showing for each month 
the percentages of beneficial, injurious and neutral spe- 
cies of insects and fruits eaten by these birds. The fig- 
ures at the right give similar percentages for all the 
birds for the entire year. Following the upper line, we 
note the small percentages of injury done in the early 
spring, the marked increase of injury in April, due to the 
excessive destruction of predaceous beetles, and the 
heavy percentages of the fruiting months. The general 
average of beneficial elements destroyed for the year is 
thirty-six per cent. On the second line we notice an in- 
verse variation. Commencing with a ratio of ninety-four 
per cent, of injurious elements eaten in February (if we 
include the larva of Bibio in these), the record runs down 
to seven per cent, in September, the general average for 
the year being forty-three per cent. 
This comparison, however, is merely a quantitative one. 
Injurious or beneficial elements are balanced against each 
