88 BIRDS IN THEIR RELATIONS TO MAN. 



cutworm-like caterpillars, formed almost nine-tenths of the 

 food for the month. 



The bluebird winters to a considerable extent in southern 

 Illinois, where its food consists very largely of wild fruits, 

 especially the berries of the mistletoe. A few beetles, bugs, 

 and spiders fill out the winter bill of fare. 



In the case of six young bluebirds yet in the nest, though 

 well feathered, Dr. Judd found that the food consisted of 

 " beetles, caterpillars, grasshoppers, spiders, and a few snails." 



Although the bluebird eats a large percentage of preda- 

 ceous and parasitic species that are often considered bene- 

 ficial to man, the probabilities are largely in favor of the 

 assumption that in devouring these the bird is assisting in 

 keeping up a proper balance of organic forces, while in eating 

 the insects injurious to crops it is doing a very great good. 

 Professor Forbes estimates that " one hundred bluebirds at 

 thirty insects each a day would eat in eight months about six 

 hundred and seventy thousand insects. If this number of 

 birds were destroyed, the result would be the preservation, 

 on the area supervised by them, of about seventy thousand 

 moths and caterpillars (many of them cutworms), twelve 

 thousand leaf-hoppers, ten thousand curculios, and sixty-five 

 thousand crickets, locusts, and grasshoppers. How this 

 frightful horde of marauders would busy itself if left undis- 

 turbed no one can doubt. It would eat grass and clover, and 

 corn and cabbage, inflicting an immense injury itself, and 

 leaving a progeny which would multiply that injury indefi- 

 nitely. 



The bluebird is easily encouraged on the home grounds 

 and will well repay a little trouble in furnishing nesting sites. 

 It breeds readily in boxes and bird-houses, and if these are 

 provided in abundance it seems likely that the numbers of 

 the birds may be materially increased. 



