No. 391.] OBSERVATIONS ON OWLS. S74 
Fisher gives the results of examination of the contents of 
92 stomachs of Aszo wilsontanus, and of 87 stomachs of A. 
acciptrinus (when we eliminate those stomachs which were 
found empty, and which probably were of birds shot in the day- 
time). I have carefully computed from Fisher’s tables for these 
two species of owls the exact number of food objects in detail 
per stomach, and the results may thus be compared with my 
data, counting in only mice, shrews, and small birds. 
A. wilsonianus “ 1.57, 2.16; birds, .o8. 
(Fisher) mice, shrews, 1.52; birds, .26. 
(mihi) í 
(Fisher) “ “ 1.78; birds, .22. 
ied aaien (mihi) t s $9; 3.25 UR, IA, i2, 
This comparison of the two sets of data would show that 
the long-eared owl probably does the greater part of its diges- 
tion, and disgorges most of its pellets on its roost. But the 
short-eared owl, since here there is a marked discrepancy 
between the figures of Fisher and myself, would appear to dis- 
gorge a smaller proportion of its pellets at its roost, and a con- 
siderable number at casual feeding perches; this is probably 
referable to the more crepuscular mode of life of the short-eared 
owl, which leaves its roost earlier in the evening, and returns 
to its roost later in the morning. The food of the short-eared 
owl is more diversified than that of the other species, probably 
due to its covering more varied feeding grounds in its hunts. 
HI. 
Finally, as to the numerical abundance of our mice and 
shrews, as deduced from the relative abundance of their re- 
mains in owl pellets. It must be kept in mind that owls hunt 
for their food mainly on open meadow and marsh land, less in 
thick woodland. Their hunting is also mainly done by night. 
Accordingly, woodland and diurnal mammals would be less fre- 
quently destroyed by them than would nocturnal mammals of 
the more open districts. But the following figures would give 
a fair comparison of the numerical abundance of such small 
nocturnal mammals as are found at night in the hunting areas 
