46 AN ECONOMIC STUDY OF FIELD MICE. 



species — the Cooper and sharp -shinned — destroy so many birds and 

 poultry as to far outweigh any good they may do. If legislation 

 against hawks is needed, which is more than doubtful, careful dis- 

 crimination should be exercised as to the species placed under ban, 

 and corresponding protection should be given those that are of un- 

 doubted benefit to the farmer. 



Owls. — Owls are preeminently enemies of mice. Their eyes are 

 adapted to twilight and nocturnal hunting, and they prey mostly 

 upon animals that are active after sunset. Xoiseless of wing and 

 possessed of sharp talons and much strength, they attack small mam- 

 mals with great success. 



Owls, and also hawks and some other birds that eat small verte- 

 brates by swallowing them entire, are unable to digest the bones, fur, 

 and feathers. These are thrown up in the form of pellets, the bones 

 being surrounded by fur and feathers. Much of our knowledge of 

 the food of owls is derived from examinations of these pellets. 



The American barn owl (St)-i.r prat in cola) is rather common in 

 the southern half of the United States, breeding as far north as forty- 

 one degrees. In part of its range field mice are common and it preys 

 upon them to a considerable extent. Examinations of 39 stomachs 

 of barn owls were made by Doctor Fisher. Of these, 1 had eaten a 

 domestic pigeon; 3, other birds; 17, mice; 17, other mammals; 4, 

 insects; and 7 stomachs were empty. Meadow mice were found in 

 9 of the stomachs. The mammals eaten, other than mice, were chiefly 

 ground squirrels (spermophiles) and other injurious species. 



Doctor Fisher records the results obtained from an examination 

 of 675 pellets of the barn owl collected at Washington, D. C. They 

 contain remains of 1.731 rodents, 56 insectivorous mammals, 32 birds, 

 and 2 frogs. The rodents were mainly rats (JIus nor regions), house 

 mice (Mus musculus), and meadow mice {Microtus). Of the last 

 there were 1,123 skulls, or an average of almost 2 to each pellet. 

 Doubtless similar investigations in California, where these owls are 

 common, would show that there spermophiles are the chief food. 



The habits of the European barn oavI (Strix aluco) serve to illus- 

 trate further the usefulness of our own bird. Dr. Bernard Altum, 

 a German naturalist, in 1863 recorded the results of examinations of 

 703 pellets of the barn owl. He found remains of 16 bats, 933 

 rodents, 1,479 shrews, and 22 small birds (19 of which were spar- 

 rows). Of the rodents 693 were voles. 1 ' Later (1867) he published 

 the results of examinations of 360 additional pellets, making 1.063 

 in all. The total shows 2,151 insectivorous mammals, and 1,801 

 rodents, of which 1,284 were voles/' 



o Science. N. S.. vol. 3, pp. 623-624, Apr. 24. 1896. 



6. Journal ftir Ornithologie. vol.. 11, pp. 41-46. 217-219, 1863. 



c Zoologische Garten, vol. 8. pp. 263-264, 1867. 



