MONTHLY WILDLIFE RESEARCH LETTER 
Department of Conservation and Natural History Survey, Cooperating 
Glen C. Sanderson and Helen C. Schultz, Editors 
Urbana, Illinois February, 1965 Vol. 8, No. 2 
1. Pheasant Populations and Land Use S. L. Etter 
At least 55 percent of the pheasants present on the Sibley Study Area during 
early fall, 1964, were not present by late February, 1965* About 19 percent of the 
population loss could be directly attributed to hunting; it was estimated that 9-5 
percent of the hens and 33*5 percent of the cocks (age-classes combined) were shot 
during the 1964 hunting season (Table 1). In view of the apparently high level of 
nonhunting losses occurring among pheasants of both sexes, possibilities for sub¬ 
stituting hunter-mortality for some of the natural mortality should be considered. 
The above estimates of population losses are conservative, because the basic 
assumption was made that the only mortality suffered by adult hens (the age-class 
used to estimate losses for all other age-classes) was a result of hunting. A 
more realistic estimate of adult hen mortality would probably range between 25 and 
35 percent for the October-February period each year; estimates of losses for the 
other age-classes would be proportionately higher. 
Changes in the composition of the Sibley pheasant population were estimated 
from the sex and age ratios of 507 pheasants trapped during October and November 
1964, the age ratios of 150 pheasants trapped during January and February 1965, ar, d 
the sex ratio of 4,532 pheasants observed on the area during January and February 
1965. 
Table 1. Relative mortality rates of pheasant sex- and age-classes, Sibley Study 
Area, October 1964 - February I 965 . 
Age-Class 
Number per 100 
in the Prehunt 
Adu1t Hens 
Popu1 at ion 
Percentage Loss 
Prehunt 
Posthunt* 
Hunting 
Unknown Causes 
Tota 1 
Adult Hens 
100 
90.5 
9-5 
? 
9-5 
Juveni1e Hens 
151 
57 
9-5 
52.7 
62.2 
Adult Cocks 
23 
7 
38.5 + 
31.1 
69-6 
Juveni1e Cocks 
149 
29 
32.8 + 
47.7 
80.5 
All Birds 
423 
183.5 
19.3 
37-2 
56.5 
* Corrected for 
a 9.5 percent i 
11 ega 1 kill 
of hens; 1 
the average estimated rate of 
illegal hen kill for 1959-62 was based on 
f 1 uoroscop 
ic examination of 
wi nter 
trapping samples. 
t Based on number of tags recovered from cocks tagged during October and November 
(1964) and known to have been shot in November and December (1964). 
1; 
r'»» 
. j M ii 
1J 1865 
