lA>vv.C_<M\ 
V'S MO.-3 
MONTHLY WILDLIFE RESEARCH LETTER 
Department of Conservation and Natural History Survey, Cooperating 
T. G. Scott, Editor 
Urbana, Illinois 
March, 1961 
Vol. 4, No. 3 
W-30-R-14 R. F. Labisky, R. I. Smith 
Data obtained by the night-light trapping of pheasants on the Sibley 
study area, 1956 through 1960, indicate that juvenile hens suffered a higher mor¬ 
tality than adult hens between fall and early winter in each year except the 
1958-59 season. 
Body weights of females trapped during October and November indicate that 
the age and subsequent weight of juvenile females during this period may be rela¬ 
ted to this mortality (Table l)• The 1958 hatch of pheasants occurred relatively 
late (mid-point of hatch, June 29-July 5), and this is reflected in the compara¬ 
tively low weights of juvenile hens in October. Weights of juvenile females in¬ 
creased from October to November of 1958 at a rate which exceeded all other years. 
It has been proposed that late hatches place a physiological stress on 
adult hens which increases the late summer and fall mortality of this age group. 
However, these data suggest that a late hatch may favor the survival of juvenile 
females and thereby more than offset the accompanying loss of adult hens. 
Table 1.— Changes in the age composition of the female segment of the 
Sibley pheasant population in relation to body weights in October and November. 
Per Cent Juvenile Hens Average Weight of Average Weight of 
in Female Population Adult Hens (gm) Juvenile Hens (gm) 
Pre- Post 
Year 
Hunt 
Hunt 
Change 
Oct. 
Nov. 
Change 
Oct. 
Nov. 
Change 
1956-57 
77.1 
65.4 
-11*7 
951 
953 
+ 2 
868 
898 
+30 
1957-58 
60.6 
50.0 
-10.6 
936 
966 
+30 
827 
875 
+73 
1958-59 
70.0 
72.9 
+ 2.9 
932 
959 
+27 
788 
884 
+96 
1959-60 
59.8 
55.3 
- 4.5 
941 
932 
- 9 
859 
866 
+ 7 
1960-61 
56.5 
43.3 
-13.2 
945 
1,016 
+71 
378 
872 
- 6 
