\). 2 . 
r> . \ O 
MONTHLY VJILDLIFE RESEARCH LETTER 
Department of Conservation and Natural History Survey, Cooperating 
T, G. Scott, Editor 
Urbana, Illinois October 1959 
Vol. 2, No. 10 
W-30-R-13 R. F. Labisky 
1959, the study of nesting ecology of pheasants on the intensively 
cultivated 23,200-acre Sibley area located in Ford and McLean counties, showed 
a decline in the production of young pheasant,; when compared to 1958 but an in¬ 
crease in production when compared to 1957 (see table l). The data obtained 
from standardized counts of pheasant broods, although influenced by many variables, 
indicated similar trends. 
Table 1.—Pheasant productivity on the Sibley area. 
Category 
1957 
1958 
1959 
Number of Nests Established Per 100 Acres 
Percentage Change Between Years 
12.4 
26.6 
+114.5 
23.6 
-11.3 
Number of Nests Hatched Per 100 Acres 
Percentage Change Between Years 
4.2 
7.9 
+88.1 
5.6 
-29.1 
Broods Observed Per 100 Miles of Roadside 
Percentage Change Between Years 
30.3 
37.5 
+23.7 
30.8 
-17.9 
W-42-R-9 R. D. Lord 
Most of October was spent trapping, marking, and releasing rabbits. 
Seventy-one were captured, marked, and released on the Allerton 4-H area and 52 
on the Sanctuary area. 
Data were analyzed in preparation for a paper to be given at the Midwest 
Wildlife Conference. Analysis of reproduction in cottontails according to age 
as determined from the lens shows that average litter size increases with age 
of the female up to 3 years, (Only 3 rabbits out of 941 attained an age of 4 
years.) Also, juveniles have the lowest prevalence of pregnancy and 1 year old 
rabbits the highest. Prevalence of pregnancy decreases slightly with increasing 
age after the first year. 
The contribution of juvenile breeding to the annual crop was only 12.28 
per cent this year as compared with 18 per cent last year. The reason for the 
drop lies in the lower proportion of juvenile breeding during July, August, and 
natural 
LI|p 
