Table 38.--A Preliminary Life Table for Caspian Terns 
Based on nestlings banded from 1926 to 191 inclusive, each age 
interval starts August 1. The mortality series (column a',) 
represents the number reported dead per 10,000 birds available 
for study at each age interval; from this, a survival series 
(colum 1',) has been constructed to represent the number known 
to be alive at the start of each age interval. | 

q ] 
Age Banded Number Mortality Survival sented ity 
Interval Birds Reported Series Series Rate (per 
(in years) Available Dead 10, 000[4x+(2)] cent per year) 
O~-1 12,091 52 43.0 97.0 bby 
1-2 12,091 17 1.1 54.0 26 
2—3 12,091 7 5.8 39.9 
h=5 12,091 5 hel 29.1 
5-6 11,032 3 2.7 25.0 
6-7 10,534 k 3.8 22.3 18 
7-8 9,631 3 3.1 18.5 
B~9 8,850 2 203 15.4 
9-10 7,465 3 Lee 13.1 
10-11 5, 88h 1 1.7 9.1 
11-12 4,811 1 2.1 Tol 
12=13 3,758 2 53 5.3 
13-1, 3,305 0 0 ) ws 
Total ~ 106 97.0 370.2 

Pacific coast; it implies that nearly 80 per cent of all the adults 
above age 2-3 would have to be successful in raising young. Both 
samples are so small that the comparison has a limited valve only. 
Theoretical populations having a straight 15 per cent 
mortality rate for all age intervals past 2=3 apparently are balanced 
by productivity only slightly lower than this one. This would permit 
a larger fraction of the adults to be either nonbreeding or unsuc- 
cessful in bringing off young. 
Published survival studies of other Laridae 
Herring Gull 
Abridged life tables have been published for Larus 
argentatus by Marshall (1$47) and by Paynter (1947, 1949). Some 
of their results are compared in table 39 along with statistics 
on the European herring gull reported by Paludan (1951). This 
90 
