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BULLETIN 621. 



natural foes. The most effectual single step is to surround the pro- 

 posed bird sanctuary with a vermin-proof fence (fig. 2). Such a 



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FIG. 2. Cat-proof fence ; a, with barbed wire ; 6, with loose overhanging netting. 



fence should prevent entrance either by digging or by climbing, but 

 will serve its greatest use if it can not be climbed, and is therefore 

 cat proof. For this purpose the erect part of the fence above ground 

 should be 6 feet high, and the weave should not be more than IJ-inch 

 mesh. The overhang should be 2 feet wide, and if strung with 

 wires these should be not more than \\ inches apart. If it is im- 

 practicable to build an impenetrable fence, the next best device is to 

 put guards (fig. 3) of sheet metal on all nesting, trees and on poles 

 supporting bird houses. This should be done in any case where 

 squirrels or snakes are likely to intrude, as it is usually impossible 

 to fence out these animals. Tree guards should be 6 feet or more 

 above ground. Attacks by hawks, owls, crows, jays, or other enemies 

 are best controlled by eliminating the destructive individuals. Those 

 who wish to combat English sparrows will find full directions for 

 so doing in Farmers' Bulletin 493. 1 



BREEDING PLACES. 



Although a considerable number of our native birds build their 

 nests on the ground, the majority place them in trees or shrubs, either 

 in holes or on the limbs or in the crotches. Shrubbery and trees for 

 nesting sites, therefore, are essential for making a place attractive 

 to birds, and a double purpose is served if the kinds planted are 

 chosen from the list of fruit-bearing species given farther on. 

 Shrubs should be allowed to form thickets and should be pruned 

 back severely when young so as to produce numerous crotches. 



Constant removal of old trees and modern tree-surgery have re- 

 sulted in a great diminution in the number of tree cavities, the natu- 

 ral homes of most of our hole-nesting birds. Fortunately, most of 

 these birds will utilize artificial nest cavities or bird houses. The 



1 Dearborn, Ned, " The English Sparrows as a Pest," revised, 1917. 



