1912] Bryant: Relation of Birds to a Graaslioppcr Outbreak 19 



deer {Oxyechus vociferus), Anthony green heron {Butorides 

 virescens antlionyi), black phoebe {Sayornis nigricans), Cali- 

 fornia horned lark [Otocoris alpestris actia), tricolored red-wing 

 {Agelaius tricolor), and cliff swallow {Petrochelidon lunifrons 

 lunifrons) . 



The efficiency of the different species, when determined by 

 destructive capacity, showed the burrowing owl to be the ablest 

 destroyer; when determined by the numbers of individual birds 

 in the territory, showed blackbirds, meadowlarks. killdeer, orioles, 

 and shrikes to take positions in the order named. 



Birds cannot be considered a dependable means of control 

 of all grasshopper epidemics, but can be inferred to be efficient 

 in the prevention of many. 



Birds can be depended on to act as defenders and protectors 

 of crops because of their warfare against grasshoppers, and their 

 value in this regard can be estimated in dollars and cents. 



Birds flocked to areas where grasshoppers were abundant. 



Birds changed their food habits and fed on grasshoppers, 

 the insect most available in this case. 



The failure of birds to check an insect outbreak is evident 

 to all. Their success in preventing insects from becoming ab- 

 normally abundant is not so apparent but is no less real. AH 

 obtainable evidence, however, points to the fact that the regula- 

 tive influence exerted by birds when insects are to be found in 

 normal numbers, although less apparent, is none the less im- 

 portant, for at such times artificial control measures are seldom 

 used. 



Certain birds, such as the blackbirds, kingbird, oriole, and 

 meadowlark, although usually condemned for their depredations 

 on crops, in this instance were praised for their usefulness. 

 Damage caused by birds at one time of the year may be more 

 than counterbalanced at another time. 



