672 General Notes. [June, 
2. Do birds prevent or restrain any oscillations of insects now 
noxious, or capable of becoming so, if permitted to increase more 
freely? That is, do they bring to bear upon any such species a 
constant pressure so great that those insects would increase 
unduly if this pressure were removed by the destruction of the 
birds ? 
3. Do they do anything to reduce existing oscillations of in- 
jurious insects? Do they sometimes vary their food-habits so far 
as to neglect their more usual food and take extraordinary num- 
bers of those species which, for any reason, became superabun- 
dant for atime? In answer to the third question the paper has 
been prepared. Mr. Forbes selected an orchard which for six 
years had been stripped by canker-worms. He shot a considera- 
ble number of birds therein for two successive years, on May 
24th, 1881, and May 2oth, 1882, representing nearly all the kinds 
seen in the orchards, made full notes of the relative abundance 
the species, examined carefully the contents of all the st 
obtained, and tabulated the results as the basis of his paper. i 
appeared that the robin and twenty-six other species of v pis 
sects, of which 16 per cent was canker-worms and only 4 Sain 
insectivorous beetles, The blue bird ate 12 per cent. of can 
worms. Mr. Forbes concludes: d habits, 
1. That birds of the most varied character an to the 
migrant and resident, of all sizes, from the tiny ate md 
blue jay, birds of the forest, garden and meatpt w 
arboreal and those of terrestrial habit, were cema i y of in- 
attracted or detained here by the bountiful supp a 
sect food and were feeding freely upon the Pe 
abundant. That 35 per cent of the food of all the h ies of 
gated in this orchard should have consisted of a single pee ae 
insect is a fact so extraordinary that its meaning Cann ssed a5 
taken. Whatever power the birds of this vicinity Pe argely 
checks upon destructive irruptions of insect life was i pa Ps 
exerted here to restore the broken balance of Oe aa of 
_ 2. The comparisons made show plainly that the as insects 
this concentration on two or three unusually nu oe their food | 
was so widely distributed over the ordinary elements @ atic 
that no especial chance was given for the rise of new | 
among the species commonly eaten. _ indigo bi i, the 
3. The fact that, with the exception of the ae with thos? 
species whose records in the orchard were compa many catet 
made elsewhere had eaten in the former situation | 
