Vol. 7, No. 11 
Page 2 
These data show that nest densities in four of these six cover types on the 
Sibley Study Area decreased from 1 96 3 to 1964; only strip cover and small grains 
had increased densities. Nest density on seeded roadsides increased from 1 96 3 to 
1964 while declining in the majority of other cover types on the study area. 
Tabie 1. Densities of established pheasant nests on seeded roadside plots and in 
six other cover types, Sibley Study Area, 1963 and 1964. Data for the six cover 
types were obtained from 100, 10-acre plots comprising a 4.3 percent sample of the 
23,200-acre study area. 
Cover Type 
Established Nests per 
100 Acres 
1963 
1964 
Seeded Roadsides 
291 
381 
Unharvested Tame Hay 
322 
281 
Strip Cover* 
154 
218 
Harvested Tame Hay 
310 
187 
Sma11 Grains 
35 
61 
Pastures 
114 
50 
Nonagricultural Areas 
30 
20 
Includes roadsides, fencerows, waterways, etc. 
3. Factors I nf 1 uenc i nq Distribution of Pheasants i n Illinois W. L. Anderson 
Analyses of data obtained during the past 5 years have revealed some inter¬ 
esting relationships between body weights and rates of survival of hen pheasants 
on the Neoga Study Area. Hens introduced at Neoga, and native hens captured on 
the area, were classified as light, medium, and heavy weight. The medium-weight 
class included all hens whose weights at the times of release were within 1 
standard deviation of the mean weight computed for adults and for juveniles of 
each strain. The light- and heavy-weight classes included the remaining birds. 
Considering the introduced pheasants, known losses were least among medium- 
weight hens, slightly greater among heavy-weight hens, and greatest among light¬ 
weight hens (Table 2). In general, this was the pattern for hens of both age 
groups of all introduced strains. However, mortality of native hens of the three 
weight classes, particularly the juveniles, was found to increase with body weight 
(Table 2). Although the ecological implications of these findings are not clear, 
they do give rise to some interesting questions. Are the losses among heavy¬ 
weight hens reared at Neoga of sufficient magnitude to prevent establishment of a 
self-maintaining population? Is the increased rate of death among heavy-weight 
hens reared at Neoga a direct cause and effect phenomenon? What factor or factors 
caused heavy-weight hens to suffer greater losses than hens in the medium- and 
light-weight classes? Is selection for a smaller pheasant taking place on the 
Neoga Area? 
