50 AN ECONOMIC STUDY OF FIELD MICE. 
100, insects; 5, spiders; 9, crayfish; 11, miscellaneous: and 43 were 
empty. A good proportion of the " other birds " were English spar- 
rows. About ;i third of the mice were identified a- meadow mice, 
while k 24 were house mice. The large proportion of insects eaten is 
remarkable. 
The burrowing owl (Speotyto eunicularia hypogcea) is a small 
species, common on Avestern plains, and noted for its abundance dur- 
ing summer in prairie-dog " towns," where it occupies the deserteq 
burrows of that rodent. Of 32 stomachs of this owl examined by 
Doctor Fisher, 2 contained mice; 1, a prairie dog; 3, lizards: 3, scor- 
pions; 1. a centiped; 30, insects, and 1 was empty. The species is 
largely insectivorous and undoubtedly highly beneficial. 
Several other species of owls occur in the United States, but at no 
season are they abundant over any considerable area. Probably all 
feed largely upon meadow mice. Doctor Fisher's report covered only 
a small series: but 6 out of 9 great gray owl stomachs, 4 out of 22 
sawwhet owl stomachs, 10 out of 38 snowy owl stomachs, and the 
single hawk owl stomach examined contained the remains of field 
mice. 
From the testimony of Doctors Fisher, Altum, Jackel, and RorigJ 
and careful observations b} T others, the great value of owls for reduc- 
ing the number of meadow mice is established beyond doubt, and the 
various species should everywhere be protected by legal enactments. 
CROWS. 
Among the most formidable bird enemies of field mice are the larger 
members of the crow family (Coriridce). The fact that ravens, 
hooded crows, and rooks in the Old World feed upon voles and lem- 
mings has often been noted. American crows have similar habits 
and feed upon field mice whenever occasion offers. Besides the 
common crow (Corrus brdchyrhynchos) the list of mouse-eating 
crows includes the fish crow (Corrus ossifragus) , the northwest crow 
(Corrus b. caurinus), the raven (Corrus corax sinuatus), and the 
white-necked raven (Corrus cryptoleucus). Magpies and the larger 
jays also destroy mice to some extent. 
The food habits of the common crow form the subject of Bulletin 
No. (') of the Biological Survey. The results of examinations of 
909 stomachs of crows are tabulated in the report. Of this number, 
78 contained mice, they being fourth in order of importance on the 
list of animal food for the year. Professor BarroAvs says : " There 
is abundant proof from several sources that crows often capture 
living mice, particularly the short-tailed field mice, which build their 
nests usually on the surface of the ground among the roots of grass. 
Here the crows discover them, and. tearing the nest to pieces, de- 
«The Common Crow of the United States, Walter B. Barrows and E. A. 
Schwartz, 1895. 
