xxxviii INTRODUCTION 



acli contents of birds shot. When these cannot be determined with- 

 out microscopes and collections of insects and seeds for comparison, 

 the stomachs should be sent for examination to Professor F. E. L. 

 Beal, of the Biological Survey, Department of Agriculture, Wash- 

 ington, D. C.i In general it may be said that the thousands of 

 stomachs which have already been examined have shown that birds 

 are divided into three classes, — 



1. Those that are injurious at all times, as the three accipitrine 

 hawks, which live mainly on small birds, game, and poultry. 



2. Those that are injurious part of the year and beneficial the 

 rest of the time^ such as blackbirds that come in hordes in the fall 

 and destroy the crops, but which when scattered out over the coun- 

 try at other times of the year do an immense amount of good by de- 

 stroying injurious insects. 



3. Those that are beneficial at all times, as many hawks and owls 

 and a large number of insectivorous and weed-seed-eating birds. 



As Professor Beal says: "If crows or blackbirds arc seen in num- 

 bers about cornfields, or if woodpeckers are noticed at work in an 

 orchard, it is perhaps not surprising that they are accused of doing- 

 harm. Careful investigation, however, often shows that they are 

 actually destroying noxious insects ; and also that even those which 

 do harm at one season may compensate for it by eating noxious 

 species at another. Insects are eaten at all times by the majority of 

 land birds, and during the breeding season most kinds subsist largely 

 and rear their young exclusively on this food. When insects are 

 unusually plentiful, they are eaten by many birds which do not 

 ordinarily touch them. Even birds of prey resort to this diet, and 

 when insects are more easily obtained than otlier fare, the smaller 

 hawks and owls live on them almost entirely. This was well illus- 

 trated during the recent plague of Rocky IMountain locusts in the 

 western states, when it was found that locusts were eaten by nearly 

 every bird in the region, and that they formed almost the entire 

 food of a large majority of the species.""-^ 



1 Tlie Survey will furnish, on application, blank schedules for recording data, tags 

 for numbering the stomachs, and franked envelopes for mailing. When collected, the 

 stomachs (crops and gizzards) should be placed in alcohol or formalin for at least a 

 week. Before forwarding to the department, they should be taken from the fluid, spread 

 out on a newspaper, and dried for several hours, then placed in a baking powder can or 

 cigar box, wrapped with a franked envelope on the outside, and mailed. The collector 

 will be reimbursed for the outlay for alcohol, and will receive five cents apiece for a 

 limited number of stomachs of certain species. 



- Beal, F. E. L., " Some Common Birds in their Relation to Agriculture," Farmer^s 

 Bulletbi, No. 54, U. S. Department of Agriculture. 



