10 



case of an irruption of an insect pest does not usually destroy 

 the pest until the injury has been done; it only prevents 

 another generation. Birds and other predatory enemies, on the 

 other hand, kill the pest at once, and so prevent both imme- 

 diate and later injury. 



Professor F. E. L. Beal, who probably examined the contents 

 of more birds' stomachs than any other scientist of his time, 

 says, "That birds are an efficient check upon insect multipli- 

 cation seems impossible of denial, and it is doubtful if any- 

 where else in the animal kingdom any other restraining influence 

 so important can be found." 1 



We must understand that birds in Nature are neither mere 

 beneficent organisms, working solely for the good of the human 

 race, nor injurious enemies of mankind; but that as a whole 

 they form a regulative body doing their part in keeping a 

 wholesome balance amongst the forces of Nature for the benefit 

 of all. To illustrate in some measure the food relations of birds 

 and the manner in which food preferences react, the following, 

 somewhat revised, is taken in substance from my " Useful 

 Birds and their Protection:" 



Eagles, large hawks and owls feed to some extent on crows, 

 and probably the nocturnal, tree-climbing, nest-hunting raccoon 

 also robs crows of eggs and young; otherwise they seem to 

 have very few natural enemies to check their increase. Crows 

 feed on so many different forms of animal and vegetable life 

 that they are nearly always able to find an abundance of 

 suitable food; therefore they are commonly and widely dis- 

 tributed. 



The general fitness of the crow is admitted by all. Un- 

 doubtedly it has a useful work to perform in the world. But 

 a careful study of its food habits shows so many apparently 

 harmful traits that it may well leave the investigator in some 

 doubt regarding the crow's value in the general plan. Crows 

 rob the nests of robins, eating very many eggs and young birds; 

 therefore they constitute a serious check on the increase of 

 robins. Robins feed largely on common black beetles, called 

 ground beetles (Carabidae). As these beetles are not quick to 

 fly by day and may be easily caught, they form a considerable 



1 Beal, F. E. L.: The Relation between Birds and Insects, Yearbook, United States Depart- 

 ment of Agriculture, 1908, p. 344. 



