84 FOOD HABITS OF THE GEOSBEAKS. ' 



more than 13 times as much as the old birds take. So wide a dis- 

 crepancy would seem to indicate that there is great difference between 

 old and young birds in the need for this material. 



Young. 



Among the blue grosbeaks examined are 13 young collected in 

 Kansas in July and August. Eight of these are nestlings, and 5 

 are young just out of the nests, but still being fed by their parents. 

 The percentage of animal food for the 13 young birds is 99.08; of 

 vegetable, 0.92. 



Grasshoppers constitute 74.1 percent of the food. Among them 

 are included the lesser migratory locust {Melanoplus atlariis) and a 

 large coral-winged locust {Hippiscus, fig. 40). The remains of as 

 many as 16 short-horned locusts were obtained from one stomach, 

 while another contained 14. Caterpillars, among them the purslane 

 sphinx, compose 10.7 percent of the subsistence of the nestlings, and 



FiQ. 40. — Coral-wlnged locust (.Hippisous tuberculatus) . (Prom Lugger, Minnesota Ex- 

 periment Station.) 



snails 10 percent. The remainder of the animal food consists of a 

 weevil, a long-horned beetle, a ground beetle, a robber fly, and the 

 eggs of a tachina fly, which were on the purslane caterpillar. It is 

 curious that^so large a proportion of the beneficial insects consumed 

 should be in the stomachs of nestlings, but it may be that these items, 

 which ordinarily are rarely taken, are hurriedly gathered only be- 

 cause of the insistent demands of the hungry young. 



The vegetable food consists of a few unidentified vegetable fila- 

 ments and some slight remains of blackberries in two stomachs; this 

 was the only fruit eaten by any of the birds, young or old. 



Summary. 



Present data shows that the food of the blue grosbeak is 67.6 per- 

 cent animal and 32.4 vegetable. 



Grain constitutes 14.25 percent of the diet, but on account of the 

 scattered distribution of the birds, no appreciable damage is done 

 during most of the summer. Later, when they forage in flocks, they 

 are said to do considerable injury. But, as noted above, the birds 

 consume twice as much animal as vegetable matter, and even if all 

 of the latter had been grain, instead of less than half, as is actually 

 the case, it would have been paid for many times over. 



