THESAUIDUBON BUCCETIN 27 
single bird’s stomach at one time.” ‘This certainly shows great capacity on 
the part of birds to control the insect situation, if left to do their work. 
In the 1911 Yearbook, it is reported that “Birds are recognized as the most 
effective natural enemies of the coddling moth. In some localities they 
destroy from 66 to 85 per cent of the hibernating larve, and their work 
in large measure accounts for the small spring broods of the insect.” From 
the same report we learn that 36 species of birds are known to prey upon 
the coddling moth. These species belong to 13 families, the most important 
being the woodpeckers, titmice and sparrows. 
Birds are busy in their work during the entire summer, early and late. 
As soon as insects are out in numbers sufficient to supply food for birds 
they begin their work of control. A fair estimate would be 120 days’ work 
each year in the state by insect eating birds. “They feed on insects a much 
longer time, but on account of the ebb and flow of that lowly life, the birds 
would average only about 120 days of full feeding time. 
During this 120 days, it may be estimated that each bird would con- 
sume nearly 250 insects, or 10,000 insect eggs daily. The figures are many 
times this number for some days. ‘The total daily consumption in the state 
would approximate 18,000,000,000 insects. Weed estimates that 150,000 
average sized insects fill a bushel measure. On this basis they would eat 
in a year approximately 360 grain elevators full of 40,000 bushels each, or 
nearly 3% elevators full to each county in the state. In other figures, 2,000 
bushels fill a freight car to capacity. Each elevator would contain 20 cars, 
so the insects consumed annually by birds would amount to three trainloads 
of 20 cars each in each county in the state. These insects, left unharmed, 
would multiply so fast that in a single season, would, in the natural course 
of events, produce over 50 times as many as the birds now eat. 
This leads us to the general statement that the birds are the natural 
check on insect life, and form the balance of power in nature. Insects feed 
on plant life and the birds may easily be pictured as the preservers and 
defenders of plant life. “They make it possible for us to grow economic 
plants. Birds are said to consume approximately 90 per cent of all insect 
life, and the State of Illinois spends annually about $10,000,000 in its war- 
fare on the other 10 per cent of insects. 
Dr. F. E. L. Beal, the noted ornithologist, so long connected with the 
United States Biological Survey, says: ““The true function of insectivorous 
birds is not so much to destroy this or that insect pest, as it is to lessen the 
numbers of the insect life as a whole—to reduce to a lower level the great 
flood tide of insect life. That this is the true relation of birds and insects 
should be inferred from the fact that the two have lived together for 
countless ages, and the balance of nature has been preserved, except as dis- 
turbed by the operations of man.”’ 
A certain per cent of insects seem quite necessary to the life of birds, 
and what is left may be considered to form the basis of a balance of power. 
