No. 4.1 BIRD HOUSES AND NESTING BOXES. 



207 



eggs and young. (See Plate V.) Nests on poles are not so often 

 visited by the foregoing enemies of birds, and such nests may be 



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BOTTON^ 



Fig. 21. — Swallow box, supposed to be cat-proof, and details of construction. 



protected against them by any one of the devices shown (Fig. 

 20). Nests on isolated trees may be safeguarded in a similar 

 manner, but in the woods protection is hopeless, and hole- 

 nesting birds, with the exception of chickadees, will rarely 

 nest there. Nesting boxes hung by wires from outer branches 

 of trees on the edge of the woods have given 

 good results in some cases. Cats cannot reach 

 these and squirrels seem not to trouble them 

 often. (See Fig. 22.) Boxes placed on poles 

 set up in a pond or on a small island bring 

 good results. 



Poles need not be more than 6 or 8 feet in 

 length, except for martins, and may be very 

 slim, made from a young pine or cedar 

 or any other sapling. They may be fig. 22. -To puzzle cats. 

 screwed to fence posts with lag screws (large screws with 

 square heads; see Fig. 23 and Plate VII., Fig. 2) so that 

 they may be taken down in the fall and stored away until 

 spring. (The barbed wire fence is best for this purpose 

 as it is not used as a highway by squirrels and cats.) 

 Where there are no fences, posts may be set in the 

 ground and the poles fastened to them. Boxes put 

 up on the walls or ridgepoles of buildings often attract birds if 

 the trees are not near enough to allow squirrels to reach them, 

 and if cats cannot get at them. (See Plate VIII.) 



Fig. 23. 



