98 BIKDS OF CALIFOENIA AFFECTING FRUIT INDUSTEY. 



The food of the bhiebird consists of elements whose consumption 

 is ahnost wholly a benefit to the farmer. Four-fifths of it is insects ; 

 only a small portion of these are useful, and these to a limited extent. 



In the investigation of the food of the bluebird 187 stomachs were 

 examined. This number is not so large as could be desired, and, 

 moreover, was rather irregularly distributed over the year. Only 

 one stomach was obtained in May, and only one in April, while the 

 number for several other months are too few. Geographically they 

 fairly well represent the fruit-growing regions of the State from as 

 far south as San Bernardino northward to Santa Rosa. The food 

 found in the stomachs consists of animal matter, 82 percent; vege- 

 table, 18 percent. 



Animal food. — Of the animal portion a little less than 12 percent 

 consists of predaceous beetles (Carabid?e), which are usually reck- 

 oned as useful. There are, however, many exceptions to this rule, 

 and since most of the sj^ecies of this family are wonderfulW abun- 

 dant it is not probable that the bluebird does much harm by eating 

 them. It is believed, moreover, that this record of'Carabidse is above 

 the normal, for the one bird taken in April had eaten 90 percent of 

 these beetles, thereby raising the average of the whole. In August, 

 on the other hand, not one of the five birds examined had eaten a 

 carabid. Had these months been omitted from the reckoning the 

 average would have been reduced to about one-third of the present 

 figure, which is probably much nearer the truth. 



Other beetles amount to over IT percent of the food, and were 

 distributed among about a dozen families, all of them harmful, except 

 three or four ladybirds (Coccinellidae), which are useful. 



Caterpillars evidently are a favorite food, and probably are eaten 

 in every month, though evidence is wanting for April and May. 

 They amount to over 17 percent of the year's food. Few of these 

 insects are eaten in spring and early summer, many in fall and winter. 

 As practically all caterpillars are harmful, this item of diet counts 

 entirely in the bird's favor. 



Grasshoppers and crickets, mostly the former, were eaten in every 

 month except April, but a greater number of stomachs would prob- 

 ably' give a different result. They amount to a little less than 24 

 percent of the year's food. They appear in the stomachs of western 

 birds at a somewhat earlier date than in those of eastern species. 

 In the Atlantic and Central States, August is preeminently the season 

 of grasshoppers, and in that month they constitute the principal 

 article of diet of many species of birds. The western bluebird eats 

 grasshoppers in March to the extent of about 11 percent of its food. 

 In June they amount to over 38 percent, and in July reach a maximum 

 of nearly 49 percent, or nearly half of all that it eats. In September 

 they amount to 40 percent, but decrease rapidly from that time. 



