l-t Vnivcrsity of California Publications in Zoology [Vol. 11 



A flock of 200 blackbirds must be, under the eireumstanees, 

 worth $20 at the minimum. If the value of this same flock of 

 blackbirds be estimated at $100 for the year, they would be 

 able to eat over twenty-five sacks of grain, and yet in the end 

 cause a saving that would more than pay for the grain. 



Some of the fallacies which can be easily pointed out in this 

 type of presentation are as follows : In the computation birds are 

 represented as being able entirely to clean up a certain area. 

 This cannot be true, for grasshoppers are taken over a large area 

 and the territory is not cleaned up systematically but enough are 

 usually left to continue some damage. This investigation showed 

 that in spite of the good work of all the birds combined, the 

 grasshoppers took the entire summer crop of alfalfa in local 

 areas. Then, too. birds do not always choose the same locality 

 where damage is done to carry on their beneficial work of insect 

 destruction. 



I would not minimize in the least the value of birds at the 

 time of an insect outbreak. The fact that the numbers consumed 

 by birds increased, together with the fact that birds flocked to 

 the infested areas, sufficiently proves their value at such times. 

 I would, however, call attention to the fact that birds are of as 

 great, if not greater, economic value when insects are in normal 

 numbers. 



It is at the time of an insect outbreak that the usefulness of 

 birds is most appreciated, because then it is most evident. Their 

 value as insect destroyers is doubtless almost as great, if not 

 greater, throughout the year when outbreaks do not occur. 



Fortunately material collected at Los Banos the same month 

 in 1911 was available for comparison. This afforded a compari- 

 son of the food of both meadowlarks and bicolored red-winged 

 blackbirds in two successive years, one without and one with an 

 outbreak of grasshoppers. As grasshoppers were far less numer- 

 ous in the summer of 1911 it has been possible to obtain in- 

 formation as to the comparative destruction by these birds when 

 grasshoppers were in relatively normal numbers, and when they 

 were in abnormal numbers. A glance at the following table shows 

 percentages of the different kinds of food taken, and the aver- 

 age number of grasshoppers taken per bird in the two years. 



