24 BULLETIN 107, U. S. DEPARTMENT OF AGRICULTURE. 



The animal portion of the food of the young Brewer's blackbird 

 at this time of the year is of economic importance and amounts to 

 nearly 94 per cent. Conspicuous are caterpillars (mostly cutworms) , 

 which totaled 34.57 per cent, or over a third of the stomach contents. 

 These insects, abundant in many fields and doubtless doing con- 

 siderable injury, together with adult Lepidoptera, occurred in 59 

 of the 78 stomachs, in several cases amounting to over 90 per cent 

 of the food. Ground beetles (Carabidae) amounted to 11.45 per 

 cent. While these beetles, as a family, are considered beneficial, 

 being mainly predaceous, there are some which injure vegetation. 

 This is especially true of the genus Amara, which made up the greater 

 portion of this part of the food. Spiders were eaten freely by the 

 nestlings and constituted 9.37 per cent of the food. Flies amounted 

 to 7.34 per cent, while the remaining animal food was divided in 

 small quantities among insects of several orders. 



The vegetable food is of little importance at this time of the year, 

 both from its character and relatively small proportion (6.08 per 

 cent). Over three- fourths was of rubbish, which testifies to the 

 voracious temperament of the young, while weeds and a little grain 

 formed the rest. 



The young Brewer's blackbirds obtained in July were fully fledged 

 and were out of the nest picking up much of their own food. Of 

 45 birds only 2 had failed to eat the weevil, and in the remaining 

 stomachs it amounted to 25.47 per cent of the food. An average of 

 11.47 adults, 0.24 pupa, and 25.53 larvae, or over 37 weevils in one 

 stage or another for every bird, was the record made by these juve- 

 nals. A few cases will illustrate the importance of these birds as 

 weevil destroyers. One had eaten 229 larvae, 7 pupae, and 20 adults : 

 another made away with 140 larvae and 6 adults, and the record of 

 a third was 4 adults and 150 larvae. The abundance of adult weevils 

 of the year's brood in the middle of July is indicated by the stomach 

 of a young blackbird, which contained 95 insects in this stage. 

 Another had captured 10 adults, 1 pupa, and 126 larvae. Other 

 interesting records are as follows: 94 adults; 1 adult and 60 larvae; 

 26 adults and 45 larvae; 21 adults and 35 larvae; 3 pupae and 63 

 larvae ; 3 adults and 50 larvae ; and 5 adults and 52 larvae. 



The weevil composed about one-third of the animal food during 

 this period, which in turn amounted to 77.8 per cent of the total con- 

 tents. Of other animal food Lepidoptera, mostly caterpillars, formed 

 13.18 per cent, a little less than two-fifths of the amount taken in 

 June. Hymenoptera, many of which were parasitic, made up 11.29 

 per cent. Hemiptera, the bulk of which was composed of the small 

 cicada, Platypedia putnami, formed 10.11 per cent. Ground beetles 

 totaled 8.67, while the remaining portion was divided in small quan- 

 tities under several heads. 



