94 The Food of Birds. 



method, and, in fact, the usual one, is that of watching 

 birds while taking their natural food in the free state. 

 Now and then a fact may be learned in this way which 

 would escape detection in any other, — such as the perfora- 

 tion of the cocoons of Cecropia by the downy woodpecker 

 reported by F. M. Webster,* — but usually this method is 

 of wholly secondary usefulness. The difficulty is very 

 great of telling with certainty, in the great majority of 

 cases, just what a bird is eating, even if one watches it 

 with a glass. The notion of the food resulting must be dis- 

 torted, as the species will be seen much more frequently 

 and clearly in some of its haunts than in others. It is im- 

 possible by the use of this method, even to guess intelli- 

 gently at the ratios of the different elements of the food — 

 a matter of the first importance to an understanding of 

 the subject. It yields very few facts for the time expend- 

 ed, and these, in nearly every instance, could have been 

 learned in much less time, with far greater certainty, and 

 in far greater detail, by the following method. Finally, 

 it affords no means of reviewing observations, but the 

 impressions received from the hasty and imperfect glance 

 of a moment must either be rejected wholly or must stand 

 as verified observations. 



By the third method, however, that of examining the 

 contents of the stomachs after death, each bird usually 

 affords a large number of objects which can be studied 

 critically, and in detail, and can be indefinitely preserved 

 for reference. These objects give a nearly or quite com- 

 plete and impartial record of the food for some hours past, — 

 those elements taken in a thicket or a tree-top being as 

 evident as those taken on open ground. They are usually 

 identifiable by the skilled student. Even very minute 

 fragments will tell as much as the out-of-door observer can 

 learn under the most favorable circumstances. In the 

 great majority of cases it is possible so far to fix the kinds 

 of food as to bring every element clearly into one of the 

 three classes, beneficial, injurious or neutral. And here 

 opportunity is afforded for careful and trustworthy esti- 



*In an unpublished paper read at the meeting of the Illinois State 

 Nat. Hist. Soc, at Bloomington, Feb., 1880. 



