191-] Bryant: Eclation of Birds to a Grasshopper Outbreak 17 



must cause some diminution in the amount of damage done, how- 

 ever slight it may be. Consequently the large numbers of grass- 

 hoppers taken by birds during the outbreak must have meant 

 a decrease in the possible damage in spite of the fact that such 

 a decrease could not be noted. 



It seems safe to say that as a natural control measiire, birds 

 must head the list. Parasites in some instances may be more 

 important than birds as natural control measures. However, 

 their influence, owing to their great fluctuation in numbers and 

 delay in their appearance until large numbei-s of their hosts are 

 assembled, does not appear to be so dependable. Birds can be 

 considered an almost constant factor and therefore must be con- 

 sidered more dependable. None of the grasshoppers collected 

 during the investigation was found to be parasitized. 



The investigation showed that the birds in the vicinity of the 

 outbreaks changed their food habits, in that they fed on the 

 insect most available. The fact that meadowlarks neglected 

 their usual percentage of ground beetles and fed almost entirelj' 

 on grasshoppers can be explained in two waj's. Either the grass- 

 hoppers were taken in preference, or they were taken because 

 they were the most easily obtained. The large number eaten 

 by the killdeer, and by the Anthony green heron, horned lark, 

 and oriole demonstrates this point, for the recorded food of these 

 birds under other conditions does not .show so large a percentage 

 of grasshoppers. 



Undoubtedl.y birds flocked to the infested areas. Brewer 

 blackbirds were seen flying out from the ranch houses to the 

 infested areas to feed. Large flocks of bicolored red-wings fed 

 almost entirely in the areas where grasshoppers were abundant. 

 A census of birds taken in infested areas, compared with one 

 taken in a non-infested district, showed birds to be about three 

 times as abundant in the infested areas during hours of feeding. 

 Certain birds examined, and found to contain but few grass- 

 hoppers, doubtless fed to a larger extent on these insects when 

 they were of smaller size. The swallows, for instance, owing 

 to their small size, are unable to eat a large grasshopper. If 

 the investigation could have covered the entire time of the out- 



