Relation of Summer Birds to Western Adirondack Forest 435 



the Raven is so rare as to be negligible, and the Canada Jay is 

 merely a chance straggler. The Blue Jay is a regular inhabitant 

 of the margins of the wood but is not numerous ; the Bronzed 

 Grackle is uncommon, and the Cowbird is apparently absent from 

 the plateau country, though it might be expected to follow the bush- 

 dwellers into the higher clearings. 



Snakes as Enemies of Birds. Another circumstance rendering 

 the western Adirondacks a desirable summer habitat for birds is 

 the comparative scarcity' of snakes. The garter snakes are not 

 greatly addicted to taking young birds, but some of the larger and 

 more aggressive species make a practice of thus adding to their 

 daily bill of fare in the bird-nesting season. Chief in the category 

 of predatory snakes elsewhere is the blacksnake, which is absent 

 from this region, as also is the rattlesnake. Most snakes feed 

 mainly on small rodents, particularly meadow mice; and these, as I 

 have already said, are few about Cranberry Lake, a. fact that may 

 partly account for the scarcity of serpents, as I suppose it does for 

 the fewness of hawks and owls. 



The Role of Predatory Species. It may not be altogether a 

 blessing to bird life when natural enemies of every kind are lacking 

 in their environment. Forbush ('16, p. 7) formulates a broad state- 

 ment on this point as follows : " It is well known to naturalists 

 that in a state of nature the natural enemies of any species are as 

 essential to its welfare as are food, water, air and sunlight." He 

 explains this principle as follows : 



(a) Natural enemies regulate the numbers of animals. 



(b) Natural enemies preserve the fitness of the animals on which 

 they prey. 



(c) Some natural enemies regulate others. 



(d) Useful species may become harmful if not held in check by 

 natural enemies. 



(e) Natural enemies supplement and check one another. 



(f) Natural enemies tend to keep the numbers of birds at their 

 normal limit. 



Forbush concludes that the natural enemies of birds are neces- 

 sary and desirable as they tend to maintain within proper bounds the 

 numbers of the species on which they prey ; he also suggests 

 judicious and moderate limitations upon the activities of the natural 

 enemies, that the biological balance may not be disturbed by man's 

 unwise intervention. 



A CENSUS OF THE BIRDS AT CRANBERRY LAKE 



A part of my plan for the season's work (1916) was a definite 

 census of the bird life of each minor habitat, and by a combination 

 of these to make an approximate estimate of the bird population of 

 the region. Great difficulties were encountered in this work. The 

 shrubbery grows breast high in all open spaces and the topography 

 is chiefly of glacial formation, with ridges and depressions strewn 

 with boulders of all sizes, the smaller ones usually hidden by bushes 



