Vo1. 14, No. 11 
Page 3 
following prescribed burning in either March or August. Twenty-three nests 
have been found in 146 acres (36 plots) during the second nesting season after 
a March burn—a density of 6.3 acres per nest. Twenty-seven nests have been 
found in 118 acres (30 plots) during the second nesting season after an August 
burn—a density of 4.4 acres per nest. By the third nesting season after a 
March burn, only two nests were found in 74 acres (22 plots)—a density declin¬ 
ing to 37.0 acres per nest. By the third nesting season after an August burn, 
however, a high density of 3.9 acres per nest was still evident (11 nests in 
12 plots totaling 42.5 acres). Up to this point, the data suggest that burning 
in August is better than burning in March for maintaining attractive nesting 
cover for prairie chickens. Limited nesting is possible during the first nest¬ 
ing season after an August burn, in contrast to no nesting, and high densities 
have resulted in both the second and third nesting seasons after an August burn, 
instead of only the second season. Incongruously, in 1971, cover available for 
the fourth nesting season after a March burn produced the good density of 5.8 
acres per nest—4 nests in 23.2 acres (6 plots). These later data preclude the 
emergence of a clear pattern. It is hoped that more data will provide a better 
basis for drawing conclusions on the longevity of the beneficial effects of 
prescribed burning on nesting prairie chickens. 
6. Rabbit Management G. B. Rose 
The annual fall censusing of cottontail rabbits on the 100-acre (40- 
hectare) study area at the 4-H Memorial Camp adjacent to Robert Allerton Park 
was conducted this year, the 16th successive year. One hundred and three 
rabbits were trapped and ear-tagged during a 10-day period at the beginning of 
November. Several population estimates were calculated from the capture and 
recapture data. The Schnabel (short form) estimate is 111 animals, the geometric 
maximum likelihood estimate (MLE-G) is 186, and the maximum likelihood estimate 
from a regression of the logarithm of the number of individuals in a frequency 
class on frequency of capture (MLE-R) is 164. The MLE-R is regarded as the 
best method of estimation. 
On November 13, Dr. H. H. Shoemaker and students from the University of 
Illinois participated in the annual “rabbit drive' 1 through the area to obtain 
an estimate of the ratio of color-marked to unmarked rabbits in the population.' 
There were 33 observations of rabbits—24 were of yellow-tailed rabbits and 9 
were of white-tailed rabbits. Hence, the Lincoln Index estimate was 120 
rabbits, with 95 percent confidence limits of 94 to 146. 
The MLE-R estimate of 164 rabbits is less than the November estimates of 
211, 278, and 193, 1968 through 1970, but is comparable to the estimate of 176 
for November 1967 . 
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