The Bird Department 



By a. a. Allen, Ph.D. 

 Assistant Professor of Ornithology, Cornell University, Ithaca, N. Y. 



THE ENEMIES OF BIRDS 



WHEN the white man first came to this country 

 and before he began clearing the forests and 

 starting the rudiments of our present agricul- 

 ture, he found what has been called a "balance of na- 

 ture." Each plant and animal in the struggle for its 

 existence and the persistence of its kind, had developed 

 a strength and a productive capacity that required hold- 

 ing in check by the struggles or foraging of other species. 

 And each species was so held in check that this balance 

 existed. While this condition endured there were no 

 weeds, no insect plagues, and no infestations of small 

 rodents. Each species increased up to the limit of its 

 food supply and then was controlled by starvation and 

 the attacks of its enemies. Insects and rodents, together 

 with the lack of sunlight due to the shadows of the 

 forests, kept the vegetation within bounds. The insects 

 and rodents were held down chiefly by the birds, and 

 an excess of birds was prevented by the carnivorous 

 animals and a few species of hawks. 



AN ENEMY OF THE BIRDS 



The raccoon is as good a climber as the cat and nearly as destructive 

 to bird life but, of course, not nearly so abundant. 



When the early settlers cleared the forests and planted 

 and cultivated their gardens, they let in the sunlight, they 

 enriched the soil and they supplied the native plants as 

 well as their crops with suddenly increased nourishment. 

 Thus they all flourished. New plants that had had to 

 starve in the old country crept in with the crops, and re- 

 sponding to the luxuriant conditions, escaped beyond con- 



trol and became "weeds." The effect on the insect life 

 was ecjually remarkable. The locust and the cricket, for- 

 merly fighting for a meager existence on the prairie grass, 

 suddenly found themselves in a Garden of Eden and 

 increased so tremendously that for a long time in the 

 Mississippi Valley, it was almost impossible to raise crops 



THE RED SQUIRREL 



friendly terms with the birds at a feeding station but individual 

 red squirrels often develop nest-robbing habits. 



of any kind. The Colorado potato beetle which had been 

 eking out its existence on a few species of plants related 

 to the potato in the Rocky Mountains, was suddenly con- 

 fronted with a perfectly inexhaustible food supply in the 

 open cultivated fields where there were no birds or other 

 enemies. Each female beetle lays so many eggs and the 

 young transform to adults in such a short time that in a 

 single season it is possible for the offspring of one pair 

 of beetles to number over sixty millions. Quick to re- 

 spond, this beetle in a very few years spread from its 

 native State all over the West and throughout the East 

 until it became a perfect scourge in all places. 



But what of the natural enemies of the insects, the 



405 



