Vol . 9, No. 1 
Page 5 
5• Responses of Prairie Chickens to Habita t Manipulation 
R. J. Ellis, R. L. Westemeier 
Studies of land use on 10 census areas totaling 76,720 acres revealed that 
the acreage of suitable nesting habitat for prairie chickens in southeastern 
Illinois continued to decline in 1965 (Table 4). Grass that is neither pastured 
nor mowed (undisturbed grass) and grass hay mowed after the nesting season, covers 
of vital importance to nesting prairie chickens, occurred on 6-5 percent of the 
acreage on the study plots in 1963 but only 2.5 percent in 1965, a decrease from 
41.6 acres of good nesting cover per section in 1 96 3 to only 16.5 acres in 1965 
(Table 5)• 
The reduction of undisturbed grass acreage has resulted primarily from the 
expiration of Federal Conservation Reserve (CR) contracts. In the six counties 
(Jasper, Wayne, Marion, Clark, Clay, and Effingham) which support the largest numbers 
of prairie chickens in Illinois, the total number of effective CR contracts decreased 
from 595 in 1 963 to 46 in 1965* In several local areas prairie chickens were be¬ 
lieved to be increasing in the early 1 96 O 1 s in response to the CR program. This is 
no longer the case. 
At Bogota, where an effort is currently under way to preserve at least one 
flock of prairie chickens in Illinois, undisturbed grass and grass hay amounted to 
4.4 percent of the 10,240-acre study area in midsummer 1965- This represents 28 
acres of nesting cover per section; however, fall plowing in 1 965 has further 
decreased this acreage, and some of the remaining fields of grass offer poor nesting 
cover because of proximity to woodland, lack of fertility, or other unfavorable 
condit ions . 
Since i 960 , 254 acres in five separate tracts were acquired for prairie 
chickens at Bogota, but only 87 acres in the refuge system will provide suitable 
nesting cover in 1 966 . Seventy-seven more acres have recently been seeded to red- 
top, but will not provide nesting cover until 1967- Thus, 164 acres cf nesting 
cover are reasonably assured for 1 967 at Bogota. If, however, adequate funds can 
be raised to purchase 300 additional acres at Bogota, the opportunity will exist for 
providing a scatter pattern of up to 554 grassland acres in eight different tracts 
by 1967- This would amount to 34.6 acres of grass per section over an area almost 
one-half township in size, which several authorities believe is the minimum size 
necessary to support a self-contained population of prairie chickens. A moderate 
degree of security would then be assured for the Bogota chickens. 
Table 4. Land use on 10 prairie chicken census areas (76,720 acres) in south¬ 
eastern) 1 1 i no i s , expressed as percentage of total area. 
Cover Type 
1963 
1964 
1965 
Row Crops 
62.5 
67-9 
70.2 
Smal1 Grains 
n .7 
12.0 
13.3 
Legume 
Hay 
2.3 
1 -5 
1 .4 
Undis tu rbed 
• 9 
.6 
• 7 
Grass 
Hay 
2.3 
1 .8 
1.1 
Undisturbed 
4.2 
3.3 
1 .4 
Pasture 
9-2 
6.1 
5-7 
Weeds 
• 3 
1 .3 
1 .0 
Trees and Brush 
4.4 
3.1 
3-0 
Other Uses 
2.2 
2.4 
2.3 
