MASON AND LEPBOY. 



19 



laboratory records, we can compound them with the figures we have 

 obtained in field observations and draw our conclusions. 



Comparative bulks of foods if expressed merely as percentages 

 are of absolutely no value whatever, and cannot give any idea as 

 to the true economic ratio of the food of the bird in question. What 

 we want to know is the exact number of grains of corn, the number 

 of insects, etc., taken, and we must not draw our conclusions from a 

 small number of records nor from a mass of records that have been 

 accumulated at one season of the year only. We must take a fair 

 average. We must consider the economic importance of each item 

 of food taken, whether the grain is of value being taken from stand- 

 ing crops or otherwise, and whether the insects and other animal 

 and vegetable food are of any importance, and if so what and to 

 what extent. We can then obtain a definite ratio between the 

 economic value of the various foods eaten, and from it draw conclu- 

 sions definitely as to whether the species of bird in question can be 

 regarded as beneficial or otherwise. 



LIST OF BIRD8 EXAMINED. 



