Vo 1. 17 , No. 7 
Page 2 
These census data were incorporated into seven weather regions for an eventual 
squirre 1-weather analysis. The weather regions formulated consist of the counties 
in the average Apri1 and May isotherms for Illinois. Minimum daily temperatures 
in April and May are of primary importance to oaks and hickories, which flower 
during these months. Fruits developing on these hardwood species during April 
and May are staples for several forest game species. 
Within the weather regions, linear correlation analyses revealed that census 
counts of 1 year were not similarly or significantly correlated with the census 
counts of the succeeding year. Linear correlations of the census data and the 
harvest indices of the number of squirrels killed per hunter trip in the fall 
preceding the census counts or in the fall subsequent to the censuses were also 
performed. The census data and the harvest data were negatively and not sig¬ 
nificantly correlated in all but one region. The census data do not appear to 
give a good indication of the next year's census count nor of the harvest trend 
for the number of squirrels killed per hunter trip. 
Responses of P rairie Chickens to Habitat Manipulation R. l. Westemeier, 
D. R. Vance 
In contrast to the 10-year period of 19&3 through 1972/ when success of the 
hatch of prairie chicken nests on sanctuaries at Bogota averaged 66.9 percent, 
and not lower than 57-1 percent, nest success dropped to 31.1 percent in 1973 ! 
The poor hatch last spring was followed by a 29.6 percent decline in the breeding 
population in the spring of 1974 . 
As of 18 July 1974, 48 nests have been located on the sanctuaries at Bogota, 
only 15 of which (31-3 percent) were hatches. Thirty-one of the unsuccessful 
nests were destroyed by predators and one was judged to have been abandoned. 
Thus, the heavy rate of predation on nests is continuing for the second consecutive 
year. Opossums, raccoons, skunks, and increasingly, coyotes, are probably the 
main predators involved in the nest destruction. 
Prairie chicken nests appear more vulnerable to predators during unusually 
wet weather, considering that the seasons for nesting in both 1973 and 1974 were 
characterized by rainfall that was well above normal. Also, the food base of 
predators continues to be low in quantity on prairie chicken sanctuaries, as the 
nests of other ground-nesting birds and the nests and sightings of cottontails 
and small mammals appear sharply reduced compared to the period of 1963 - 72 . 
Other studies have suggested that high populations of buffer species result 
in increased numbers of predator hours in a given field and therefore that the 
"finds" by predators of food items such as prairie chicken nests, which remain 
stationary for about 40 days or more, must increase in direct proportion. Our 
data, however, do not support this contention. It seems to us that the low 
quantity of buffer species, combined with excessive rainfall, has resulted in 
the more intensive exploitation of the prairie chicken resource by predators. 
