Adii'oidack Birds in their Relation to Forestry. 19 



the bark of a valuable tree and the larvae which hatch therefrom 

 find this tree a source of food and protection, man designates this 

 an "injurious insect." Fortunately there are usually other 

 creatures which feed upon these so-called injurious ones and keep 

 them in check, and it is in this capacity that the birds find their 

 field of usefulness. 



In the perfect forest there is an exact balance between all these 

 combating elements, and the proper proportions exist so that the 

 beneficial factors control and check the injurious agencies. When 

 this balance is disturbed either way the general equilibrium of the 

 forest is upset. If the insect-eating inhabitants are removed an 

 "insect calamity " is inevitable, or it may occur that an animal, 

 which under restraint is beneficial, becomes a pest when unre- 

 strained. 



In nature the ideal balanced condition never actually exists, yet 

 in an undisturbed forest the combating forces are so nearly 

 balanced that marked disturbances are unknown. It is only 

 when man enters with his axe, gun and tinder box that serious 

 difficulties arise. In keeping with the growth of scientific wood- 

 craft, it should then be the aim of every forester to carry on his 

 work with the minimum disturbance of natural conditions. 

 Possessed of the knowledge that all things in a forest have a rela- 

 tion to it, either for good or bad, the forester should know well 

 and study carefully all these influencing elements so that he may 

 assist the good in overcoming the bad. 



It is to the credit of scientific workers that many of these 

 factors, especially fungi and insects, have been studied with the 

 aim of finding means for their control, but it is to their discredit 

 that the important work which birds do in the protection of the 

 forests has been largely overlooked, and that these feathered 

 friends of forestry have received little aid from man, and ineffi- 

 cient protection from their host of enemies. 



It is as consumers of injurious forest insects that the birds find 

 their chief commercial function in the forest, yet the aesthetic 

 benefits accruing from their presence and cheering song should 

 not be overlooked. 



Available figures on the bird consumption of forest insects are 

 not obtainable, but a few figures given by Mr. E. H. Forbush, 

 Ornithologist of the Massachusetts Board of Agriculture, will give 

 some idea of the insect capacity of one of our smaller Adiron- 



