26 BIRDS IN THEIR RELATIONS TO MAN. 



sive rather than extensive. In the preliminary stages of our 

 knowledge the miscellaneous collection of bird stomachs from 

 all parts of the country at all seasons of the year is a neces- 

 sary and useful step. The results thus obtained in regard to 

 many species are of great value, but in the case of others, 

 notably those of doubtful utility to man, — as, e.g., the fly- 

 catchers mentioned above by Dr. Palmer, — they must be 

 supplemented by careful studies on the intensive plan. An 

 excellent example of this is Dr. S. D. Judd's notable study of 

 the food preferences of the cat-bird, 1 and other studies of the 

 same sort are being made by Dr. Judd and other members of 

 the Biological Survey on a farm near Washington controlled 

 by the Survey. 2 



It was long ago pointed out by Forbes that many of the 

 most important problems in economic ornithology rested at 

 bottom upon the science of entomology. And in the diffi- 

 cult and perplexing problems that arise in the case of many 

 species a fuller development of entomological knowledge is 

 greatly needed. One of the most important of these topics 

 is that of the relation of parasitic insects to each other and 

 to their hosts. 



The discussion in this chapter has been purposely re- 

 stricted to the development of our knowledge of the more 

 general economic relations of birds. For a history of the 

 various special phases of the subject — game, eggs, feathers, 

 guano, introduction of foreign birds — the reader is referred to 

 Dr. Palmer's article in the Yearbook of the Department of 

 Agriculture for 1899. 



1 American Naturalist, vol. xxxi. pp. 392-397. 



1 See "Birds of a Maryland Farm," Bulletin No. 17, Division of Bio- 

 logical Survey. 



