NATURAL HISTORY SllRvn 
JUN 11 1982 
MONTHLY WILDLIFE RESEARCH LETTER 
Illinois Federal Aid Projects W-66-R, W- 87 -R, and 
Department of Conservation and Natural History Survey, 
Glen C. Sanderson and Eva Steger, Editors 
W-88-R 
LIBRARY 
Cooperating 
Champaign, Illinois 
May, 1902 
Vol. 25, No. 5 
Ma nipulation of Pheasant Habitat ~ W-66-R 8* E. Warner 
Last month (MWRL 25(4):l) we presented data regarding rates of observations 
for pheasants captured and backtagged on the Sibley Study Area (SSA) during the 
fall, 1962-65. Inferences were made concerning the importance of weight, molt 
characteristics, chronology of hatch, and age when captured relative to the 
survival of hens through at least 1 January. This month we will consider the 
importance of egress as indicated by these data. 
The SSA is a 6 x 6-square-mile block. The capture location for each bird 
may be classified as being in the 4 (2x2) center sections, the 12 intermediate 
sections (surrounding the center), or the 20 perimeter sections. The location 
of capture was found to be the most important variable (IP < 0.001) in the 
regression MAN0VA analysis of factors influencing rates of observation. 
Observation rates for hens captured and released in the center, intermediate, 
and perimeter sections of the SSA are compared in Table 1. For both juvenile and 
adult cohorts, observations declined from the center to the border of the SSA; 
no attempts were made to observe marked pheasants beyond the border. Although 
rates of observation were higher for adult hens (Table 1), observation rates 
declined similarly for both age cohorts from center to intermediate to perimeter 
sections. 
As a minimal estimate of egress, we compared the numbers of backtagged 
pheasants observed in each of the 3 capture-release areas on the SSA (center, 
intermediate, and perimeter) with expected numbers if the observation rate for 
the entire study area was the same as for the center. In other words, we 
assumed that observation rates of 33.5% for juveniles and 59*3% for adults 
(Table 1) reflect what occurs without egress. Actual numbers of pheasants 
observed compared with numbers expected indicate that a minimum of 31% of the 
juvenile and 29 % of the adult hens moved off the SSA during the observation 
period. 
The ratios of marked to unmarked animals are commonly used as a basis for 
estimating the population levels on a given area. This method assumes that an 
insignificant number of marked individuals move off the area after capture. 
This assumption is apparently not plausible for pheasant populations on the 
SSA, particularly during fall and winter. Perhaps most interesting is the fact 
that rates of egress for juvenile and adult hens were nearly identical. 
