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MCNTMY WILDLIFE RESEARCH LETTER 
Department of Conservat• or: and Natural History Survey, Cooperating 
61en C. Sanderson, Editor 
Urbana, Illinois June, 1966 Vol . 9, No. 6 
1* Pheasant Populations and Land Use W. J. Francis, S. L. Etter 
An analysis was made of the accuracy obtainable in searching 100 ten-acre 
plots on the Sibley Study Area for pheasant nests. The amount of hay (an important 
pheasant nesting cover) on the sample plots in I 965 was so low that it was not 
believed to be an adequate sample, so the analysis was carried out for the data 
obtained in 196*+ (Job Completion Report W- 66 -R- 5 , Job No. 2, July 15, 1965 ). 
The Poisson distribution is a fair approximation of the distribution of 
organisms randomly spaced in a medium. For the purpose of calculating accuracy 
limits obtainable for a given sample size in a general case, we assume that the 
number of pheasant nests found in a sample of a cover type follows the Poisson 
distribution, in which the limits of accuracy are given by the equation 
d* = -t 2 X 
n 
where d *= + the 95% confidence limits of X. 
t, = statistical value corresponding to 95 % confidence = 2 . 00 . 
X *= observed mean nest density in a cover type (nests per acre), 
n = area of sample in a cover type (acres). 
The observed 1964 values of n and X, the calculated value of d, the percentage 
accuracy (d/x) and the total number of nests in each cover type with the 95 % 
confidence limits indicated on the above assumptions are given in Table 1. Row 
crops (corn and soybeans) are not included since no nests were found in these 
cover types. 
Table 1. Pheasant nesting density -- Sibley Study Area, 1964. 
Cover Type 
Acres 
(n) 
Nests per 
Acre 
(x) 
95% 
Confidence 
Limits 
(d) 
Percentage 
Accuracy 
(d/K) 
Number 
of 
Nests* 
Small grains 
80 
0.61 
0.17 
28 
49+14 
Hay 
44 
1.92 
0.41 
21 
84+18 
Pasture 
41 
0.50 
0.22 
44 
20+9 
Strip Coyer 
37 
1-99 
0.50 
25 
79+20 
Non-agricultural 
44 
O .36 
0.18 
50 
16+8 
* Estimated for a 
random sample 
of n acres. 
NATURAL liiSTflilY SURifEl 
i 
JUL 11 1366 
