Vo]. 18, No. 1 
Page 3 
Responses of Prairie Chickens to Habitat Manipulation R. L. Westemeier, 
D. R. Vance 
Our continuing study on the nest ecology of prairie chickens also pro¬ 
vides basic information on the ecology of other species of wildlife that 
make use of sanctuary grasslands. Since 1963 , an average of 410 acres of nest 
cover has been systematically searched for nests annually during June, July, 
and August. In addition to prairie chickens, which suffered poor seasons for 
nesting in 1973 and 1974 (MWRL 17(9):2-3), the nests of ground-nesting species 
including quail, pheasant, mourning dove, upland sandpiper, meadowlark, 
grasshopper sparrow, cottontail rabbit, and small mammals (prairie vole and 
southern bog lemming) were all sharply reduced in number in 1974. Over the 
past 12 years, averages of 21 quail nests, 13 dove nests (ground nests only), 
60 meadowlark nests, 28 cottontail nests, and 2,135 small mammal nests have 
been found annually. However, in 1974, nest numbers were as follows: quail, 
9; dove, 3; meadowlark, 28; cottontail, 1; and small mammal, 574. The first 
pheasant nest on sanctuaries at Bogota was found in 1969 , and since then 
between 4 and 10 pheasant nests have been found annually. 
On the basis of nests per acre, the above seven species (including prairie 
chickens) of ground-nesting birds were collectively 26 percent lower in 1974 
than in 1973 and 17 percent lower than the 12-year mean. Cottontail nests per 
acre were 1,233 percent lower in 1974 than in 1973 and 1,900 percent lower 
than the mean for 7 years (1968-74). Densities of small mammal nests were 11 7 
percent lower in 1974 than in 1973 and 260 percent lower than the mean for 9 
years. 
By contrast, nest densities for seven species of birds that do not nest 
directly on the ground, including short-billed marsh wren, red-winged black¬ 
bird, dickcissel, field sparrow, Henslow's sparrow, song sparrow, and goldfinch 
plus aboveground nests of doves, were, collectively, 3 percent higher in 1974 
than in 1973 and 34 percent higher than the 12-year mean. The largest and most 
meaningful samples among the off-ground nesters were those of the redwing, 
dickcissel, and field sparrow, with mean annual numbers of 239> 42, and 11 
nests, respectively. 
We believe that the sharp difference between nest numbers of on- and 
off-ground nesting fauna on sanctuary grasslands is largely a reflection of 
the extremely wet and therefore unsuitable conditions prevalent in 1973 and 
1974 for species that nest directly on the ground. The on-ground nesters 
with their eggs and young likely constitute a much larger total biomass for 
predators than do the off-ground nesters. The relative stability or increase 
noted in off-ground nesters would not compensate for the declines in the on¬ 
ground nesters. Therefore, the net effect confronting the predator population 
would be a reduced prey population. Concomitant with the reduced food base 
for predators in 1973 and 1974 have been the highest rates of predation on 
prairie chicken nests since the project began in 1 963 • 
