Io6 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 eifectively 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 aff"ected 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 - 

 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. 



"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 eff'ect 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 sa.y, the abnormal pressure put upon the canker worm 



