Vol. 11, No. 2 
Page 3 
5- Responses of Prairie Chickens to Habitat Manipulation R. L. Westemeier 
Prairie chicken habitat is commonly thought to consist of large, unbroken 
expanses of native prairie or domestic grassland with few sharp breaks between 
different cover types. While this may be true in the colder and drier portions 
of the range of the greater prairie chicken, it appears that proximity to field 
edge is important to nesting hens under current conditions in Illinois. During 
the period 1963-67 at Bogota, a sample of 64 prairie chicken nests had a median 
distance of 27 yards from nest site to nearest field edge. The distances ranged 
from 0 to 154 yards. Two-thirds of the 64 nests were in the outer 50 percent 
(acreage basis) of the fields in which they were located. Cover types in which 
the nests were found included redtop, timothy, fescue, wheat stubble-clover mix¬ 
tures, annual weeds, and weedy corn stubble. 
Further analysis of these data revealed apparent differences with respect 
to age and type of cover. For example, median distances, in yards, from nest 
sites to nearest field edges were 41.0 (17 nests), 35-0 (4 nests), 29.5 (2 nests), 
and 21.0 (17 nests) for redtop stands in their 2nd, 3rd, 4th, and 5th year (or 
older) of growth, respectively. Four nests in lst-year redtop had a median dis¬ 
tance of only 14 yards. Thus, with the exception of lst-year redtop, both a 
progressive decline in nest densities as described previously (Monthly Wildlife 
Research Letter 10(10):3) and a progressive shift of nesting hens to field edges 
can be expected with increasing age of redtop sods. Prescribed burning and de¬ 
layed hay harvesting, as well as periodic plowing and reseeding, are among possible 
rejuvenation techniques which need to be tested on sanctuary grasslands. 
6. Rabbit Management j. a. Bailey, J. C. Hanson 
Biologists in Missouri have described ulcerative enteritis as a disease in 
the cottontail rabbit. The disease can be caused by intraspecific stress due to 
crowding. Among its symptoms are profuse diarrhea, gastric ulcers, and enlarged 
adrena1s. 
In Illinois, experience with caged and penned cottontails had produced little 
evidence of ulcerative enteritis. During the past 2 years, effects of crowding 
upon male rabbits have been studied in four experiments using six outdoor pens. 
Most of this research has been conducted by Mr. Raymond Schroeder, a former student 
assistant with the Section of Wildlife Research. 
Wild male rabbits were 1ive-trapped and placed in the pens in groups of two 
or four animals per pen. Supplemental food was provided while the rabbits were 
in the pens for from 30 to 58 days. At the end of each of the four experiments 
all the animals were collected and autopsied. Pooling the data for all experi¬ 
ments produced 20 animals kept two per pen and 40 animals kept four per pen. 
The average ratio of the fresh weight of both adrenals to body weight for 
rabbits kept two per pen was 20.1 (10 ). For rabbits kept four per pen the 
average ratio was 18.4 (10 5). The difference between these averages was a 
likely result of chance. (The probability of obtaining as large or a larger 
difference was about 30 percent.) Thus, there was no evidence that crowding, in 
these experiments, affected the sizes of the adrenal glands of the male cotton¬ 
tails. 
