Family Strigidae (Other Owls) 
Great Horned Owl 
Literature on Productivity and Survival 
The average number of eggs laid by Bubo virginianus is said 
to fluctuate regionally and perhaps annually (Bent 1939; 302, 329). 
According to Baumgartner (1938), the usual number is 2, full sets of 
one being frequently found in Florida, and sets of 5 to 6 occasionally 
reported from central and western North America. 
Nothing appears to have been published on the age at which 
this species begins to breed. When one considers the great size of 
these birds, it is possible that they do not nest until at least 2 
years old. 
Banding Work 
Great horned owls had been banded and recovered in 35 dif-~ 
ferent provinces and states up to July 30, 1946. The largest numbers 
of recoveries (among 162 records of adults and young initially examined) 
were from Alberta (20), Michigan (1), and Ohic (1C). Among the banders, 
those with the largest numbers banded were C. R. Berry of Wyoming (57), 
R. H. Pough and cooperators (56), and George Wagner and cooperators 
(3h). From 1926 to 1941 (inclusive) 55 banders, ringing 476 nestlings, 
got 113 recoveries. This is a recovery rate of 23 per cent. About 
400 more horned owls were banded by other persons who either got no 
recoveries whatever or who worked with adult birds. 
Characteristics of the Sample 
In spite of the smallness of the sample, horned owl recoveries 
in the aggregate (table 50) display something of the autumal frequency 
peaks found in so many other species, but the monthly distribution of 
mortality reports is rather well spread out throughout the year. The 
samples are too small to show significant differences between types 
of recovery, but there is some indication that the proportion of birds 
shot in the fall is about the same for young as well as adults. In 
constructing some preliminary life tables for this species, I used 
all 3 types of recovery. All the owls in these samples were banded 
as nestlings. Use of captured birds in the life tables is carried 
out with the assumption that capture in this species is virtually 
synonymous with death. 
Abridged Life Table 
A preliminary life table for subadult and adult great horned 
owls is given in table 51. Because the annual mortality rates of 51 
(for juveniles) and 23 per cent (for adults) are based on only 58 birds, 
the results will have to be confirmed by subsequent analysis of a larger 
11, 
