Vol. 8, No. 6 
Page 2 
Table l. Status of pheasant nests on manipulated and on managed control foadside 
plots along 8 miles of roadway, Sibley Study Area, June 30, 1963; June 26, 1964; 
and June 26, 1965- 
Status of 
Nests 
■ ■ --- 
Number 
of Nests 
Seeded Plots 
Managed Control 
Plots 
1963 
1964 
1965 
1963 
1964 
1965 
Hatched 
9 
4 
8 
4 
1 
2 
Active 
1 
5 
4 
1 
3 
6 
Abandoned 
and/or 
Destroyed 
17 
43 
23 
22 
29 
14 
Tota l 
27 
52 
35 
27 
33 
22 
3. Factors Influencing Distribution and Abundance of Pheasants W. L. Anderson 
Several investigators have suggested that late-summer mortality among adult 
hen pheasants might be of sufficient magnitude in some years to suppress materially 
the fall population of this species. Mortality of adult hens is reportedly 
associated with stresses arising from nesting and brood-rearing activities, and 
subsequent molt. It was therefore speculated that, if late-summer losses of adult 
hens were excessive and/or recurred frequently, they might play an important role 
in preventing the establishment of pheasants on the Neoga Study Area, located south 
of the range now occupied by this species. One manifestation of excessive losses 
of hens in late summer would be the occurrence of an atypically high number of orphan 
broods, especially during the latter part of the brooding season. Data obtained 
by observing broods at Neoga from i 960 through 1964, however, indicated that broods 
not accompanied by hens did not occur in disproportionately high numbers (Table 2). 
Ninety-three percent of 89 broods less than 6 weeks of age, observed in both early 
and late summer, were accompanied by hens. Although reduced, the proportion of 
older broods accompanied by hens was not atypically low; hens in the established 
pheasant range begin leaving their broods when the chicks are 6-8 weeks old. When 
each age-class was considered separately, the proportion of older broods accompanied 
by hens did not decrease with any degree of consistency as summer progressed. When 
ail age-classes were considered collectively, the proportion of broods accompanied 
by hens decreased from June to August (Table 2). It seems probable that this 
decrease was caused primarily by hens abandoning their broods, whose average age 
increased as summer progressed, and not by excessive losses among the hens. These 
findings suggest that the rate of mortality among brooding hens in late summer is 
no greater at Neoga than within the established pheasant range and is therefore 
probably not an important factor in preventing the establishment of self-maintaining 
populations of pheasants in south-central Illinois. 
