48 



enemies of birds. They are active, also, in limiting to harmless 

 bounds the many creatures on which they prey. 



Owls destroy great numbers of nocturnal creatures, such as 

 rats, mice and the larger night-flying insects. Both hawks and 

 owls render valuable service to the farmer by holding in check 

 the increase of small mammals, such as squirrels, gophers, 

 lemmings, wood mice and field mice. These little animals are 

 not very destructive when in normal numbers, but field mice, 

 for example, are very prolific, each pair producing a large 

 number of young each year. They breed so rapidly that unless 

 held in check they soon overrun the country, destroying grass, 

 grain, trees and practically every green thing, also the eggs of 

 game birds and other ground-breeding birds. 



The majority of the hawks and owls spend most of their 

 feeding hours in hunting for and destroying such small mammals, 

 and their capacity for such food is enormous. Lord Lilford re- 

 ports that he has seen a pair of barn owls bring food to their 

 young seventeen times within half an hour, and that he fed 

 nine mice in quick succession to a young barn owl two-thirds 

 grown. 1 As the owls throw up the indigestible parts of their 

 food, pellets composed mainly of fur and bones may be found 

 in the vicinity of their nests or roosts. In 1890 a pair of barn 

 owls occupied a space in the upper part of a tower in the 

 Smithsonian Institution at Washington, District of Columbia. 

 An examination of 200 of the pellets found there gave a total of 

 454 skulls. There were remains of 225 field mice, 2 pine mice, 

 179 house mice, 20 rats, 6 jumping mice, 20 shrews, 1 mole and 

 1 vesper sparrow. 2 Mr. O. E. Niles asserts that he found 113 

 dead rats on the ground below a great horned owl's nest, and 

 several more in the nest. Their skulls had been opened and 

 their brains removed. 2 



The young of hawks and owls remain a long time in the nest 

 and require a great quantity of food. Dr. A. K. Fisher of the 

 Biological Survey examined the stomach contents of 690 hawks 

 and owls from various parts of the United States, and con- 

 cluded, as a result of these examinations and correspondence 

 with many observers, that most hawks are more or less bene- 

 ficial to agriculture, and most owls are exceedingly useful birds. 



i Tegetmeier, W. B.: The Field [London], Vol. LXXV, No. 1956, June 21, 1890, p. 906. 

 * Fisher, A. K.: Hawks and Owls of the United States, Bulletin No. 3, Division of Orni- 

 thology and Mammalogy, United States Department of Agriculture, 1893, pp. 136, 176. 



