BIRDS IN RELATION TO AGRICULTURE 183 
Although, as I have already pointed out, the majority of 
hawks are useful birds, several species are destructive to 
bird life and should be dealt with accordingly. Among the 
destructive species are the following: Cooper’s hawk, the 
sharp-shinned hawk, the pigeon hawk, and the duck hawk. 
Fortunately these species are not very abundant. 
3. PROVISION OF FRUIT-BEARING TREES AND SHRUBS 
The vegetable food of many of our insectivorous birds 
under natural conditions consists largely of wild fruits and 
berries. Such birds as robins and bluebirds eat a greater 
proportion of animal food during the spring and summer, 
but as insects become less abundant and wild fruits ripen 
in the fall, vegetable food appears to predominate. When 
man changes the natural environment by planting culti- 
vated fruits, such as cherries, currants, raspberries, and 
strawberries, birds such as robins are apt to prefer the larger 
and more succulent cultivated varieties to the wild ones. 
When this happens the owner of the fruit is apt to forget 
the benefits that the birds have conferred upon him earlier 
in the year by destroying the insect enemies of his crops, and 
is apt to deal with them accordingly. There are, however, 
alternative methods of preventing such damage. I have 
already pointed out that it is cheaper to protect cultivated 
fruit trees against the attacks of useful birds such as robins, 
than to permit insects to increase uncontrolled by birds. 
Another method of reducing the damage done by birds to 
cultivated fruits is to provide them with wild fruits as a 
small return for their services in destroying injurious insects. 
The planting of fruit-bearing trees and shrubs in gardens 
and parks and bird sanctuaries is a very effectual method 
of attracting birds to a place. Lovers of birds and gardens, 
when planting gardens and parks, should, therefore, give 
preference to those species of trees and shrubs that bear 
