18 University of California Publications in Zoology [Vol. 11 



break, it would probably have been found that certain birds were 

 far more efficient destroyers when the insects were small than 

 when they became large. 



The stomach examination brought out clearly the warfare 

 which is waged by l)irds on insects, when the latter become ab- 

 normally abundant. Tlie destruction which actually goes on is 

 too little appreciated. More records of the good work accom- 

 plished could be made available if people would observe more 

 closely. Information as to the exact regulative influence of 

 birds in keeping the numbers of insects below the point where 

 they cause damage, is very desirable. This can be determined 

 only by cooperative observation of many intelligent observers, 

 especially at times of insect outbreaks. 



My sincere thanks are due Professor C. A. Kofoid and ilr. 

 Joseph Grinnell, of the University of California, for their helpful 

 criticism of the present paper. 



SUMMARY 



An investigation into the relation of birds to a grasshopper 

 outbreak was carried on at Los Banos, Merced Count}', Cali- 

 fornia, July 11 to 17, 1912. 



Grasshoppers were found to be causing considerable damage 

 to alfalfa and vegetables. An infestation of about fifteen grass- 

 hoppers to the square yard appeared to be necessary to cause 

 noticeable damage. In the infested areas, the grasshoppers were 

 computed to number from twenty to thirty to the square yard. 



Observation showed the following species of birds to be feed- 

 ing on grasshoppers : bieolored red-wing {Agelaius phoeniceus 

 calif amicus) , western meadowlark {Sturnella neglecta), Brewer 

 blackbird {Euphagus cyanocephalus) , Bullock oriole (Icterus 

 bullocki), western kingbird (Tyrannus verticalis), California 

 shrike (Lanius ludovicia7iiis gambeli), and the English sparrow 

 (Passer domesticus). 



Stomach examinations showed all those observed to feed on 

 grasshoppers to be effective destro.yers of the pest, and also 

 demonstrated that the following birds were also feeding on grass- 

 hoppers : burrowing owl (Speotyto cunicularia hypogaea), kill- 



