io 6 
Recent Literature. 
[April 
and take extraordinary numbers of those species which, for any reason, 
become superabundant for awhile? The present paper deals with the last 
of these questions, showing to what extent birds depart from their usual 
practices when confronted with an uprising of some insect species, and 
how they concentrate for its suppression. The paper is very carefully 
worked up to show how effectively birds may restore a disturbed balance 
of life. 
An orchard of forty-five acres was selected as the field of operations. 
It had been infested with canker worms for about six years. “As a result 
of their depredations, a considerable part of the orchard had the appear- 
ance, from a little distance, of having been ruined by fire. Closer exam- 
ination of the trees most affected showed that the branches, stripped of 
almost every vestige of green, were festooned with the webbing left by the 
worms. To the webs the withered remnants of the leaves adhered as they 
fell, the very petioles having been gnawed off at the twigs. Not one per 
cent of the trees were uninjured, and these were invariably on the outer 
part of the orchard. Those which had been attacked several years in j| 
succession were killed; and there was a large area in the midst of the 
orchard from which such trees had been removed. One did not need to 
enter the enclosure to learn that the birds were present in extraordinary 
numbers and variety. From every part of it arose a chorus of song more 
varied than I had ever heard in any similar area at that season of the 
year.” In this place, May 24, 1881, 54 birds of 24 species were taken, and 
7 other species were noted. At a second visit, May 20, 1882, 92 birds of 
31 species were shot, and 4 other species were seen. 
This was the material upon which Professor Forbes worked, the exact 
examination of the stomachs being the basis of the paper. The whole 
subject is carefully discussed, three facts standing out very clearly as the 
results of these investigations. 
u i. Birds of the most varied character and habits, migrant and resi- 
dent, from the tiny wren to the blue-jay, birds of the forest, garden and 
meadow, those of arboreal and those of terrestrial habit, were certainly 
either attracted or detained here by the bountiful supply of insect food, 
and were feeding freely upon the species most abundant. That 35 per 
cent of the food of all the birds congregated in this orchard should have 
consisted of a single species of insect, is a fact so extraordinary that its 
meaning cannot be mistaken. Whatever power the birds of this vicinity 
possessed as checks upon destructive eruptions of insect life, was being 
largely exerted here to restore the broken balance of organic nature. And 
while looking for their influence over one insect outbreak we stumbled 
upon 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 insects was so widely 
distributed over the ordinary elements of their food that no special 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 
