88 'fhe Food of Birds. 



and one-half million dollars to the permanent value of our 

 property ; or if, as is in fact a most moderate estimate, we 

 should succeed in increasing the eiRciency of birds five per 

 cent., we should thereby add eight and one-fourth million 

 dollars to the permanent wealth of the state, provided, as 

 before, that birds do not eat unduly of beneficial species. 



These figures will be at once rejected by most natural- 

 ists as absurdly low. The young robin of Prof. Treadwell 

 (a bird whose fame has extended over both hemispheres) 

 required not less than sixty earthworms a day to keep it 

 alive. A pair of European jays have been found. Dr. 

 Brewster informs us, to feed their brood half a million 

 caterpillars in a season, and to eat a million of the eggs in 

 a winter. I have myself taken one hundred and seventy- 

 five larvae of Bibio from the stomach of a single robin, and 

 the intestine probably contained as many more. 



Compared with these numbers, my two thousand four 

 hundred insects a year for each bird seem certainly many 

 times too few ; and similar criticisms might very probably 

 be made on other items of the estimate. I prefer, howev- 

 er, to put these matters with a moderation which will com- 

 mand general assent, especially as we see that the im- 

 portance of the subject does not require exaggeration. Of 

 course the individual farmer or gardener could, by intel- 

 ligent and careful management, if he knew just what to 

 do, increase the value of his own birds far beyond his indi- 

 vidual share of the above-mentioned aggregate. 



The subject has, also, a considerable scientific interest. 

 Since the struggle for existence is chiefly a struggle for 

 subsistence, a careful comparative account of the food of 

 various competing species and genera, at different places 

 and seasons and at all ages of the individual, such as has 

 not heretofore been made for any class of animals, cannot 

 fail to throw much light upon the details, causes and ef- 

 fects of this struggle. The flexibility of the food-habits 

 of the widely ranging species, the direct effects of normal 

 departures from the usual average of food elements upon 

 the origin of variations, and the general reactions of birds 

 upon their organic environment, are examples of subjects 

 upon which light should be thrown by this investigation. 



