48 
AN ECONOMIC STUDY OF FIELD MICE. 
Essex, in 1581, by saying: " ^\' 1a I < * 1 i vermin by policie of man could 
not be destroyed, till at the last there (locked together such a number 
of owles as all the shire was not able to yield, wherein' the marsh 
holders were shortly delivered from the vexation of the said mice." 
Similar testimony as to the efficiency of owls as destroyers of voles 
is contained in other chronicles, and in the account of later out- 
breaks the species is*definitely stated to be the short-eared owl. 
The short-eared owl inhabits the temperate parts of both conti- 
nents. In each its range extends northward well be}^ond the Arctic 
Circle. It is an irregular migrant and always appears in large num- 
bers where voles, lemmings, or other mice become unusually abun- 
dant. It nests on the ground in tall grass, usually in moist meadows, 
a habitat peculiarly fitted for the operations of this consumer of 
meadow mice. Doctor Fisher reports the results of examination- of 
101 stomachs of this species. Of these, 11 contained small birds; 
77, mice; 7, insects; and 14 Avere empty. In the 77 stomachs that 
contained mice fully a hundred field mice were identified. Doctor 
Rorig examined 51 stomachs of this species and found in them re- 
mains of 90 injurious rodents, of which 76 were Microtus. He ex- 
amined also 480 pellets of this owl, finding remains of 3 beetle^. 9 
small birds, 7 bank voles, 22 Microtus agrestls, and 842 J/, arvalis. 
For purjDOses of comparison, the results of the examinations of owl 
pellets are here presented in tabular form. The figures, disregarding 
fractions, represent the average number of individual mammals and 
birds found in 100 pellets of each species of owl. 
Barn 
owl. 
Long-eared owl. 
•i 
© 
| 
,cj 
; u 
- 
M 
be 
* 
*-■> 
y. i- 
~ 
.~ 
■~ 
- 
B 
it 
~'- Z * 
— 
*\ 
_ 
'■Z 
s 
1 & 
Kind of mammal or bird found 
i— i 
<< 
(£ 
B — 
*^ 
~ 
in owl pellets. 
a 
t 
^ 
- ~ 
< 
- 
s£ 
O 
P 
2 
O 
j_- 
tl 
.~ 
"~-' 
p 
^ 
25 
3 
a 
~ s 
8 
i 
s 
s 
. 
=c 
1 
- .r- 
.§ 
- 
c 
2 
S-s 
33 
'j$ 
83 
r 
~ 
1 
- 
X 
Harmful rodents: 
87 
48 
s; 
56 
16 
10 
2 
o 
166 
121 
139 
•211 
114 
182 
168 
180 
Other roden ts 
3 
a 4 
«1 


a 8 
a 2 
"1 
Insectivorous mammals (shrews, 
moles, and bats ) 
8 
202 
80 
29 
52 
1 
3 
i) 
Small birds (sparrows, etc. > 
5 
3 
(*) 
11 
26 
2 
1 
2 
'(Bank voles {Evotomys). 
b Not given. 
The barred owl (Syrnium varium ) is larger than the species 
already considered. It resides throughout eastern North America 
from Nova Scotia to the Gulf and westward to the treeless plains. 
It usually lives in rather dense forests and swamps and nests in hoi 
