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United States Department of the Interior 

 Bureau of Biological Survey 



Wildlife Leaflet 3S-162 



Washington, D. 



C. * 



May 1940 



BIRDS AS A FACTOR IN CONTROLLING- INSECT DEPREDATIONS 



1/ 



By Clarence Cottam and Francis M. Uhler, Biologists, Section of 

 Food Habits, Division of Wildlife Research 



That North American birds are regarded as a priceless national heritage 

 is shown by the fact that all but a relatively few species (or groups) arc 

 protected by Federal law, by international treaty with Canada (Great Britain) 

 and Mexico, or by the laws of the States or the Canadian Provinces. 



Birds are useful as protectors of crops and forests through their feed- 

 ing on destructive insects, as part of Nature's great balancing mechanism, 

 as scavengers, as game, food, or articles of commerce, or merely as objects 

 of beauty and interest. To a people of sentiment, wildlife or other 

 objects of nature need not bo associated with the dollar sign in order to 

 receive protection and encouragement. We agree with Emerson that "if eyes 

 were made for seeing, then Beauty is its own excuse for being." The 

 esthetic and recreational values of birds, though largely intangible, are 

 just as real as bank accounts or interest on stocks and bonds. Like a 

 masterpiece of art or an orchestral symphony, they uplift the soul and give 

 meaning and purpose to life. Man is rejuvenated both in spirit and in body 

 by a day afield, enjoying the charm and beauty of the songs of birds, stuc. 

 ing the grace and rhythm of their movements, and partaking of their contagious 

 joyousness. E. H. Forbush has well said that "the beauty of birds, the music 

 of their song, the weird wildness of their call, the majesty of their soar- 

 ing flight, and the mystery of their migration, always have be:n subjects of 

 absorbing interest to poets, artists and lovers of nature." Certainly no 

 of the appeal, beauty, and charm of literature, art, and music would be lost 

 if shorn of their allusions to birds. 



Although their esthetic and recreational worth constitutes, perhaps, 

 their greatest value to mankind, birds have also tremendous economic poten- 

 tialities to which consideration must be given. Probably more than half 

 the food of the 1,400 species and varieties of North American birds con- 

 sists of insects. That the aggregate number of insects consumed is enor- 

 mous no one can question. Yet the significance and effectiveness of such 

 feeding as a factor in insect control are matters far more difficult to 

 appraiso. Ordinarily, climate, disease, and parasites are equally or pos- 

 sibly more important as natural checks on most pest species of insects, but 

 entomologists and ornithologists agree that the insectivorous birds, through 



1/ Presented at the technical session of the Fifth North American 

 Wildlife Conference, Washington, D. C,, March 20, 1940. 



