100 ANIMAL BIOLOGY 



nesting places of bluebirds, wrens, tree swallows, and martins. 1 

 (Fig. 77.) 



1 For other methods of encouraging birds see Weed and Dear- 

 born, "Birds in their Relations to Man," pp. 304-315. Trafton, 

 "Methods of Attracting Birds," and leaflets of National Associa- 

 tion of Audubon Societies, 1974 Broadway, N. Y., e.g. No. 16 (Win- 

 ter Feeding of Wild Birds) and No. 18 (Putting up Bird Boxes), 1 

 cent each. 



