Under these conditions, the young undergo an annual mortality rate 
of about 69 per cent (125 + 180). One important condition assumed 
here is that the population is remaining stable threughout the 
period of study. Because the best available sample for study here 
included birds only banded from 1926 to 1933, the shortness of 
this period should alert us to the possibility that the actual popu- 
lation from which these banding records originate may not necessarily 
be a stable one. 
Another questionable point involves an age ratio of 1.8 
young per adult on September 1. A ratic of 1.6 is also possible. 
This would result in an estimated mortality rate of 66 per cent 
for the young birds, instead of the 69 per cent above. 
Similarly, if the adult mortality rate is about 50 per 
cent per year in this species (table 33, part B), juvenile mortality 
rates can be expected to lie between 69 and 72 per cent according 
to the two age ratios we have been considering for birds alive on 
September 1. The evidence we have available thus points to a 
mortality rates of about 70 per cent for young birds from September 
1 to August 31, and to adult mortality rates of the order of 50-55 
per cent per annum. 
Percentage taken by hunting.--The possibility of a stable 
population here at least permits us to explore certain other parameters. 
Granting that juveniles are 2.3 times more vulnerable than adults 
are to the gun and that 4.2 times as many young are shot than adults, 
it can readily be shown that a 20 per cant adult hunting mortality 
rate will yield a series of statistics that satisfy the various age 
ratics we have determined. This in turn implies a 45 per cent hunt- 
ing mortality among birds of the years 
No. Young No. Adult Ratio Yg/Ad. 
Alive at Start (Sept. 1) 180 100 1.81 
Per Cent Shot Hunting 5% 20% 203-1 
Number Shot 82 20 h.l~1 
Number Alive (Feb. 1) 98 80 1.2-1 
Bar cent Dying Nonhunting Ty LS 
umber j onhunti Es 
Number Alive Auge 31 r ce ig i25a1 
Total Dying Year 125 5 
Mortality Rate 69% 55% 
These computations were carried outas though all hunting 
mortality occurs at each age level before any nonhunting mortality. 
This of course does not happen in nature. During the years when 
these banding data were accumulated, about 78 per cent of the hunt- 
ing mortality suffered by juveniles took place between September 15 
and October 31. Only 7 per cent of the juvenile kill was recorded 
in December and January. For the adult redheads, these statistics 
19 
