CALCULATIONS. 209 



their usefulness, are indeed the most ignorant of them. 

 They attribute to them a full moiety of the injury oc- 

 casioned by insects; yet there is not an insect in exist- 

 ence which is not the natural food of certain birds, and 

 which would multiply to infinity if not kept in check by 

 them. 



Men are willing and eager to keep dogs and cats, to 

 feed and protect them, and endure their annoyances, be- 

 cause they understand that their services in a variety of 

 ways, both in the house and out of doors, are sufficient to 

 compensate for all their mischief and their trouble. They 

 can appreciate their value, and are willing to overlook 

 their offences. But the birds, who sing and make them- 

 selves agreeable in thousands of ways, men will destroy, 

 because they are either too ignorant or too stupid to 

 understand the benefits they derive from them. Probably 

 the cats and dogs in this country cost in the aggregate 

 a million of dollars in feeding them, to say nothing of 

 their troublesomeness, to one hundred dollars which the 

 whole feathered tribe costs us by the fruit and grain they 

 damage and consume. 



Calculations have been frequently made to ascertain 

 the probable amount of insects consumed by any single 

 bird. Many of these accounts are almost incredible, yet 

 the most of them will admit of demonstration. Two dif- 

 ferent methods have been adopted for ascertaining these 

 fects. The investigators watch the birds, to learn their 

 food by their habits of feeding or foraging ; or they de- 

 stroy single birds at different times and seasons and exam- 

 ine the contents of their crop. Mr. Bradley, an Eng- 

 lish writer, mentions a person who was led by curiosity 

 to watch a pair of birds that were raising a young brood, 

 for one hour. They went and returned continually, bring- 

 ing every time a caterpillar to the nest. He counted the 



journeys they made, and calculated that one brood did not 



14 



