JacccV • 
JAN 81982 
u«» 10V 
MONTHLY V'lLDLIFE RESEARCH LETTER 
Illinois Federal Aid Projects W-66-R, V'—37”^» and -R 
Department of Conservation and Natural History Survey, Cooperating 
Glen C. Sanderson and Eva Steger, Editors 
Urbana, Illinois 
December, 1331 
Vol. 24 , Ho. 12 
iianipulation of Pheasant Habitat - W-66-R R. E. l/arner 
The number of pheasant chicks that survive from hatch to early autumn 
apparently has declined in the last few decades according to recent censuses. 
On the Sibley Study Area (SSA), the mean number of chicks observed per brood 
was 6-7 during 1336-53, 5*6 during 1960-64, approximately 4 during 1965 * 69 , 
and 3*4 chicks during the 1970's. These data--particularly the declines through 
the late 1350's and early lS) 60 's--are corroborated by counts made, in. the central 
counties by the Department of Conservation. 
Survival studies on the SSA have indicated that mortality of juveniles has 
traditionally been extensive during the fall. For example, during 1962-66 an 
average of 44% of the juvenile hens survived from October to February. The 
more recent decline in the survival of chicks during summer may be coupled with 
relatively low rates of survival during fall. If fall survival data from the 
SSA during the 1960's are valid for current populations, only 1 of 4 female 
chicks hatched per nest may survive to winter. This hypothesis may explain in 
part the slowness of pheasants in easfcentral Illinois to recoup numbers lost 
in recent severe winters. (MHRL 24(10) :1). 
It is difficult to make an in-depth study of chick survival. The low 
numbers of pheasants on the study area prohibit investigative procedures that 
require large samples to test hypotheses. However, the potential causes of 
decreased chick survival have been explored by monitoring brood size, and by 
small-scale studies of the use of cover by broods, pesticide metabolization, 
nutrition, and predation. These studies will be reported in future newsletters. 
C. M* Hixon, 
L. P. Hansen 
VJe concluded last month (MKRL 24(1 1):2) that mast abundance did not cause 
the variability in recapture rates of fox squirrels during the 7-year study at 
the Vermilion River Observatory. Social factors have been implicated by 
numerous researchers in the regulation of rodent population size. Apparently, 
aggressive behavior by adult residents, especially during the breeding season, 
reduces survival in an area of subordinate, usually young, animals. Although 
few data are available, it is generally thought that these young disperse. 
Ecology and Management of Squi rrei s - V/-66-R 
