1914] Brijant: Economic Slofici of the ^y(\slct■n. Mcadoirlark 397 



quently an investigation into the relations of the birds of the 

 state to agricultural and other interests was instituted. 



The institution of the investigation was largely due to the 

 interest and energy of Mr. John P. Babeoek, Chief Deputy of the 

 California State Fish and Game Commission, 1910-11, and 

 Professor Charles A. Kofoid of the Department of Zoology of 

 the Universitv of California. 



A COMPARISON OF METHODS IN ECONOMIC 

 ORNITHOLOGY 



The attempt to show the amount of the different kinds of 

 food contained in the stomachs of birds has led to the use of 

 two distinct methods, both of which must be considered valuable, 

 and both of which approximate the end sought. A method 

 introduced by King (1883), and later used by Newstead (1908), 

 gives the total number of birds taking the different kinds of 

 food compared with the total number of stomachs examined. 

 The second method, employed by the United States Biological 

 Survey, depends entirely upon the comparative volume of the 

 different kinds of food found in the stomach, calculated in per 

 cent of total volume and averaged. A third method, in which 

 actual counts of the insects found are made, has been used in a 

 few instances (Mason and Lefroy, 1912; Fisher, 1893). Workers 

 in this field in Great Britain have used the numerical system 

 almost entirely, depending for a criterion upon the number of 

 birds taking a certain kind of food. 



Since all of these methods appear to furnish certain infor- 

 mation not furnished by the others, a combination of all three 

 methods has been used in this investigation. Dependence is laid 

 on the first method for an idea of the percentage of birds of a 

 species feeding on a particular insect, on the second for an idea 

 of the comparative amounts of the different kinds of food taken 

 by individuals and by the species, and on the third for an idea 

 of the actual numbers of the different elements of food. The 

 counting of weed seeds and insects found in the stomach of a 

 bird is difficult and fruitful of error. Yet the fact that smaller 



