20 Forestry Qiiarterly. 



dack birds. According to his authority an examination of the 

 stomachs of four chickadees revealed the presence of 1,028 eggs 

 of the canker worm. The stomachs of four other birds of 

 the same species contained about 600 eggs and 105 female 

 moths of the canker worm, the average number of eggs in each 

 of the moths being 185. Since it is estimated that a chickadee 

 will eat at least 30 female canker worms per day, it follows that 

 5,550 of these noxious insects would be destroyed per bird every 

 twenty- four hours. 



Dr. A. D. Hopkins, authority on forest insects, states in his 

 report on " In.sect Enemies of the Spruce in the Northeast," that 

 " in hundreds of infested trees examined at least one half of the 

 beetles and their yonng had been destroyed by birds and in many 

 cases it was evident that even a greater proportion had perished 

 from this cau.se alone." The woodpeckers were foremost in this 

 good work. He estimates also that 100 beetles exist per square foot 

 of the bark on an average infested tree, and as each tree is 

 covered by some 60 .squaie feet of infested bark, it is possible for 

 each tree to support 6,000 individual beetles, 100 trees 600,000, and 

 so on. If the present number of birds is able to destroy one half 

 of these beetles, it is apparent that legislation or any scheme of 

 protection which will increase their number in even a slight de- 

 gree, will materially decrease the number of ravaging insects. 

 This becomes the more important when we recall that the beetles 

 are able to overcome the resistance of a healthy living tree only 

 when present in large numbers. These figures, while only ap- 

 proximations, go to show .something of the enormous influence 

 the birds exert in keeping in check the myriad of injurious in- 

 sects which abound in field as well as forest. The money value 

 they represent is beyond computation, yet it certainly runs far 

 into the millions ainiually. Indeed, the statement so often made 

 that without birds as in.sect de.'^troyers the earth would not long 

 be habitable, is not beyond belief when we consider mathematically 

 the rate at which insects multiply when unrestrained. 



The matter appears in even a stronger light when we realize 

 that about nine-tenths of all animal forms are insects, and that 

 the disproportionally small number of birds is the only power 

 which keeps them in check. The capabilities of the birds in a 

 definite region acquire also a greater significance if the following 

 somewhat hypothetical case be considered. At a low estimate each 



