Vol. 18, No. 5 
Page 2 
number of squirrels. Therefore, there must be sufficient life-supporting elements 
remaining in the timber sale area to support this density of squirrels. The 
timber cutting did result in increased mortality or in shifts of home range for 
some of the resident squirrels, but 18 months after the sale, squirrel numbers 
have stabilized at precutting levels. 
Responses o_f Prairie Chickens to Habitat Manipulation R. L. Westemeier, 
D. R. Vance 
The annual booming ground surveys were conducted on seven areas in five 
counties of south-central Illinois in the spring of 1975. A total of 175 
prairie chicken cocks was counted on these seven areas. This total includes 
the flock at Bogota whose status was reported in the April issue of the MWRL. 
The two flocks dependent on sanctuaries in Marion County increased 24 
percent from 38 cocks in 1974 to 47 cocks in 1975- The flock near Farina 
increased from 25 cocks to 35 cocks. The flock near Kinmundy-Forbes Park de¬ 
clined from 13 cocks to 12 cocks. 
The four remaining flocks not associated with sanctuaries declined 22 
percent collectively from 1974 to 1975- The flock near Mt. Erie in Wayne 
County declined from nine cocks to eight cocks. The Clay County flock near 
Bible Grove dropped from eight cocks to four cocks. The flock near Hoyleton 
in Washington County declined from 10 cocks to 9 cocks. A new booming ground 
was located near New Minden in Washington County about 4 miles west of the 
Hoyleton booming ground. Five cocks were counted on this new ground. Excluding 
the previously uncensused New Minden flock, the total state population of 
prairie chickens diminished by 18 percent from 1974 to 1975. The flocks 
associated with sanctuaries in Jasper and Marion counties constitute 85 percent 
of the known statewide population of prairie chickens. 
In general, the small flocks outside the main sanctuary area at Bogota fared 
better than the Bogota flock. The difference is probably due to the small numbers 
of birds involved in the outlying flocks. The hatching of only one or two 
clutches would probably be sufficient to maintain populations at such low levels. 
Such small flocks could not contribute importantly to the total biomass available 
to nest predators. Prairie chicken nests would be so few and probably so 
scattered that they would not be readily found by nest predators. 
The Bogota flock, on the other hand, is large enough to provide readily 
available prey. In fact, the density of prairie chicken nests on sanctuaries at 
Bogota exceeded by 15 percent (1973) and by 42 percent (1974) the density of 
nests of all other ground-nesting birds combined. Other ground-nesting species 
include quail, pheasant, mourning dove, upland sandpiper, meadowlark, and grass¬ 
hopper sparrow. As previously reported (MWRL 18(1):3), predation rates on 
prairie chicken nests at Bogota in 1973 and 1974 were the highest recorded since 
the project began in 1963. 
