460 University of California PuhUcations in Zoologij [Vol. 11 



than they did when they were not so abundant. The results of 

 stomach examinations follow : 



Food of Western Meadowlark at Los Banos, Merced County, 

 California 



Average 

 no. of Total 



grass- per cent 

 Number Animal Vegetable hoppers gras.";- 



of birds Date food food per bird hoppers 



10 July 11, 22, 1911 99.0 1.0 7 83.1 

 5 July 1.5, 17, 1912 99.2 .8 16 96.2 



Meadowlarks took very nearly the same percentage (99, 99.2 

 per cent) of animal food each year at the same .season, showing 

 that at this time of year the bird is almost wholly insectivorous. 

 The availability of gras.shoppers as a diet appears to have influ- 

 enced the birds taken in 1912, for they averaged sixteen grass- 

 hoppers apiece as against seven taken by birds collected in 1911. 



As the numbers of grasshoppers in 1911, compared with the 

 numbers in 1912, is not definitely known, it is impossible to state 

 whether these birds changed their food habits in response to the 

 extreme availability of the insects in 1912. It is also impossible 

 to state whether the numbers taken in 1912 were in direct pro- 

 portion to the numbers taken in 1911 or whether they failed fully 

 to respond to the change in insect population. The fact remains, 

 however, that meadowlarks. and other birds as well, took greater 

 numbers of grasshoppers when they were abnormally abundant, 

 but also forsook certain articles of diet, such as beetles and weed 

 seeds, thus causing an increased percentage of grasshoppers to 

 be taken as food. The direction of the change of food habits 

 was certainly coincident with the direction of change in food 

 supply. 



The efficiency of a bird as an insect destroyer at the time of 

 an insect outbreak is governed more largely by the numbers of 

 birds than by their individual capacity. This was conclusively 

 shown in the investigation of the grasshopper outbreak. The 

 comparative destruction of grasshoppers per day by single indi- 

 viduals and by the total number of each species is represented 

 in the following table: 



