compensations have been made, however, for banding that occurred during 
the hunting season. The higher recovery rate for Canadian-banded 
adults, as compared to that for Canadian-banded juveniles, should be 
noticed. This result is directly the reverse of the evidence of 
juvenile vulnerability to the gun obtained in large-scale bandings in 
Illinois (Mann, Thompson, and Jedlicka, 197; Hawkins, personal com- 
munication). The lowered recovery rate for Canadian juveniles could 
be explained as a predation effect: if these Canadian young birds are 
at least as vulnerable as those banded in northeastern Illinois, we 
can say of the recovery rates that 
the rate for Illinois adults : the rate for Canadian adults 
e rate for nois juveniles e expected ra r an young 
From table 55, it follows that 
6.3% . 9.9% x = 12.41% 
. ( x 
Now if 12.41 is the percentage expected from (say) 100 birds at the 
time of banding, and 9.0 is the percentage actually obtained, then 
nonshooting mortality must have reduced the 100 to some new figure y 
at the start of the hunting season, it would appear then that 
12.41 _ 9.0 y = 73 
y 
In other words, decimating factors quite apart from hunting inflicted 
a mortality of about 27 per cent (i.e., 100 minus 73), from the time 
the birds were banded to the start of the hunting season. If the vul- 
nerability of Canadian-banded juveniles is really higher than that of 
Illinois-banded juveniles (as I suspect), then the nonhunting mortality 
here computed is too low. 
These computations are wholly erroneous if the Canadian 
panders failed to report all the adult mallards they banded. This 
possibility was thoroughly explored by checking the number of bands 
issued to the banders against the number they reported to have used. 
Although a number of clerical oversights were encountered, the skep- 
ticism was without basis in the present connection. 
Regionally, the best agreement between fluctuating seasonal 
recovery rates was found in the samples for adults and for all-age 
groups (figures 13 and 14). The latter, of course, are larger in 
size, more statistically reliable, and free of the impediments of 
age determinations. The banding by Ducks Unlimited (Canada), being 
scattered through the southern parts of Alberta, Manitoba, and 
Saskatchewan, is more apt to be free of local mortality influences 
than the other samples. It is of some interest that ducks banded 
on a Federal refuge in North Dakota showed the highest recovery rate 
in these samples. The implication, of course, is that a Federal 
refuge does not necessarily place ducks out of reach of hunters. 
128 
