Table 49 .—-An Abridged Life Table for Barn Owls 
Birds banded as nestlings. The first age interval starts as of 
date of banding. Columns d', and 1', were calculated to two 
decimal places and then rounded off. This has left minor dis- 
crepancies in the survival series, which represents the number 
alive at the start of each age interval and is computed directly 
from the mortality series. The mortality series represents the 
number recovered dead per 1000 banded birds available at 
age interval. tilled 
1 
(T) ) (2) (dy) (Ih) (ax) 
Age. No. Shot Banded Mortality Survival Mortality Rate 
Interval or Birds Series Series (per cent 
in Years. Found Dead Available 1000 +(2) per year) 


O-1 59 901 65.5 113.4 58 
1-2 13 901 lek 7.9 
2-3 8 901 8.9 33.5 
3-4, 7 901 7.8 24.6 
ye5 \ 901 bel 16.8 28 
Sab 1 83h, 1.2 12.4, | 
6-7 a 732 le 11.2 
7-8 2 588 3.4 9.8 | 
89 af 492 2.0 6.4 
9-10 1 479 2.1 ely 
10-11 ae 437 2.3 2.3 i 
Total and Mean - 113.4 282.7 Lo 


undoubtedly mathematical fine points that are beyond my comprehension 
in this comection, but it is hard to believe that unrecorded juvenile 
mortality is creating an important bias here. Cannabalism among the 
young is, however, a phenomenon that would leave no trace in banding 
records. It is known to occur in this species, but its extent remains 
to be quantitatively determined. 
(3) That Gallup's productivity data are atypical of the rest of the 
continent. To check this, the Fish and Wildlife Service files 
were studied to determine what brood sizes were definitely men- 
tioned by banders in their reports. These compare to Gallup's 
data as follows: 
Size of Brood 123 h4 5 6 7 Total No. Broods 
Other banders 2 56 9 7 6 1 36 
The available evidence certainly indicates that l can be regarded 
as the typical brood size for this species in North America. — 
lil 
