290 ENTOMOLOGY 
whose exhaustive tables the following food-percentages are 
taken : 
Birds Examined. Insects. Canker-worms. 
Robin, 9 93 4 oir, 
Catbird, I4 98 15 
Brown Thrush, 4 O4 12 
Bluebird, & 98 ee 
Black-capped Chickadee, 2 100 61 
House Wren, 5 ont 46 
Tennessee Warbler, I 100 80 
Summer Yellow Bird, 5 O4 67 
Black-throated Green Warbler, 1 100 70 
Maryland Yellow-throat, 2 100 37 
Baltimore Oriole, 3 100 40 
To quote Forbes: “ Three facts stand out very clearly as 
results of these investigations: 1. Birds of the most varied 
character and habits, migrant and resident, of all sizes, from 
the tiny wren to the blue-jay, birds of the forest, garden and 
meadow, those of arboreal and those of terrestrial habits, were 
certainly either attracted or detained here by the bountiful 
supply of insect food, and were feeding freely upon the species 
most abundant. That thirty-five per cent. of the food of all 
the birds congregated in this orchard should have consisted of 
a single species of insect, 1s a fact so extraordinary that its 
meaning can not be mistaken. Whatever power the birds of 
this vicinity possessed as checks upon destructive irruptions of 
insect life, was being largely exerted here to restore the broken 
balance of organic nature. And while looking for their in- 
fluence over one insect outbreak we stumbled upon at least two 
others, less marked, perhaps incipient, but evident enough to 
express themselves clearly in the changed food ratios of the 
birds. 
“2. The comparisons made show plainly that the reflex effect 
of this concentration on two or three unusually numerous in- 
sects was so widely distributed over the ordinary elements of 
their food that no especial chance was given for the rise of new 
fluctuations among the species commonly eaten. ‘That is to 
say, the abnormal pressure put upon the canker-worm and vine- 
