42 an Economic sii-dv of hkli> mice. 
row or shock. While they seldom eat rats or house mice, they some- 
time become very fond of field- mice and learn to hunt them inde- 
pendently. A good rat dog is undoubtedly a valuable assel of the 
farm, and I have known one to keep premises clear of blown rats 
(Mas norvegicus) when adjoining farms were overrun with them. 
Many cats are good mousers, both in house and field. Some live 
largely upon pocket gophers, ground squirrels, and field mice. Un- 
fortunately, however, when cats roam afield they learn to destroy 
song birds, young poultry, and game. The ordinary farm cat is 
exceedingly destructive to small birds and game, and the number that 
cats annually kill is immense. 
House cats usually are too well fed to make good mousers, and 
are believed to aid in the spread of infectious disea>es among human 
beings. In spite of the usefulness of individual cats in destroying 
mice, every community would be better off for a large reduction in 
its feline population. 
Birds that Destroy Field Mice. 
Many species of birds destroy rodents. Among those that eat field 
mice are shrikes, cuckoos, crows, herons, bitterns, storks, ibices. 
gulls, hawks, and owls. Unlike the mammals already named, some 
of these birds live almost exclusively upon field mice, and hence are 
of great assistance in reducing their numbers. 
1URDS OF PREY. 
At the head of the list of bird enemies of field mice stand the 
hawks and owls. Most of the species habitually feed upon rodents, 
a few of them almost entirely. Moreover, the species that feed lead 
upon harmful rodents feed largely upon insects. Thus the beneficial 
character of hawks and owls as a group is beyond question. 
Fortunately the economic status of American hawks and owls 
does not rest upon mere theory or general assertions without proof. 
Bulletin No. 3 of the Biological Survey a deals with the food habits 
of hawks and owls of the United States, and is based upon examina- 
tions of nearly 2,700 stomachs. Such large series of the more com- 
mon species were examined that further investigations can but con- 
firm and emphasize the present verdict — that American hawks and 
owls, as a whole., are among the best friends of the farmer and that 
only a few species are more harmful than beneficial. 6 
« The Hawks and Owls of the United States in their Relation to Agriculture 
by A. K. Fisher. M. D.. Washington, 1803. 
& Doctor Fisher's report on the food of hawks and owls has long been out of 
print For this reason some of the more important summaries of results. 
especially those relating to the mammal food, are given in this paper. Circular 
(II. Bureau of Biological Survey, Hawks and Owls from the Standpoint of the 
Farmer, gives a brief summary of the original report by Doctor Fisher, and 
may be had on application. 
