Vo1. 8, No. 5 
Page 5 
R. J. Ellis 
5. Responses of Prairie Chickens to Habitat Manipu1 ation 
Prairie chicken numbers in Illinois have been so reduced (Monthly Wildlife 
Research Letter, April, 1 965 ) that the success of each nest is very important if 
the species is to be preserved in Illinois. To increase the number of successful 
nests on the Bogota Area, the Illinois Department of Conservation provided funds 
for leasing those portions of fields where prairie chicken nests would otherwise 
be destroyed. The Natural History Survey operated a flush bar which was driven 
over each fie<d considered for leasing, so that only fields containing active 
prairie chicken nests would be leased. 
Wheat stubble fields totaling 262 acres were searched with the flush bar from 
May 1 to May 14, 1965- Most of these fields also contained stands of red clover. 
No prairie chicken nests were found. Likewise, 10 acres of undisturbed tall fescue 
yielded no prairie chicken nests. 
The flush bar was also operated in a 6-acre field of second-year timothy. 
Previously, the farmer had plowed a 2-acre strip in the center of this field and 
thereby destroyed a nest containing five eggs. The 2-acre strip of timothy south 
of the plowed portion yielded no nests. The remaining unplowed strip yielded one 
nest with 11 eggs before one-eighth of the field had been covered. The remainder 
of the strip was not searched for fear of disturbing other nests. The unplowed 
strip of timothy containing the nest was leased by the Illinois Department of 
Conservation. 
6. Rabbit Management J* 4. Bailey, R. J. Siglin 
October populations of cottontail rabbits on the Allerton Park 4-H Area were 
much larger during the years 1956 through I 96 I than during 1962 through 1964 
(Monthly Wildlife Research Letter, November, 1964). During the first 6 years, 
October populations averaged 3l*+ rabbits; during the last 3 years, about 130 rabbits. 
It has been assumed that changes in the habitat have been responsible for this 
change in the cottontai1-productivity of the 4-H Area. A specific assumption has 
been that some important component of the habitat is no longer present in sufficient 
quantity to maintain the October 1956-61 level of cottontai1-productivity. 
Habitat changes on the 4-H Area during the 1956-64 period were assessed by 
examining aerial photographs taken each year in late summer. There appears to 
have been no sudden change in the habitat that would account for the sudden change 
in fall populations between 1 96 1 and 1962. Changes seem to have been gradual and 
due to plant succession. (Sudden changes in the habitat that were not detectable 
on nonstereoscopic aerial photographs may have occurred.) 
Habitat changes on the 4-H Area were quantified by examining the 1956, I 960 , 
and 1964 aerial photographs. The habitat was divided into broad vegetat'on-types 
and the amount of each type present on the area in each year was noted (Table 5)• 
The major change has been a decrease in the amount of land supporting stands of 
annual weeds and an increase in the amount of land supporting stands of trees in 
various stages of crown-closure. Apparently, stands of annual weeds have been 
important to reproductive success and/or to survival of juvenile rabbits on the 
