Vol. 18, No. 9 
Page 4 
In recent years, fall-plowing of harvested acreages has increased, with 
a resultant loss of food supplies for squirrels and other wildlife. Thus mast 
failures may now be of more importance to squirrels than in past years. In 
1973> there was a general mast failure over much of central and northern 
Illinois. In an upland oak-hickory forest in Vermilion County, located in 
east-central Illinois, the number of acorns and hickory nuts trapped per seed 
trap declined from an average of 4.2 per trap in 1972 to 1.8 in 1 973 . Re- 
P I°?o^ t,0r \ b y f ° X sc > uirre,s was sharply curtailed on this area in the sprinq 
of 1974. Only 33 percent of the adult females had spring litters in I 974 
compared with an average of 76 percent for 1971-73- Hunters reported poor 
squ.rre hunting in central and northern Illinois in 1974, which we attributed 
to the low number of juvenile squirrels available during the hunting season. 
It thus appears to us that knowledge of the general size of the fall mast crop 
is necessary to future management of the squirrel population. 
The relationship of mast crops to squirrel populations can be investigated 
nrare intensively ,f the investigation is applied to a squirrel population of 
known composition. We recommend that the Department of Conservation Survey and 
larh"Sn °i eC ,i conduct mast surveys on selected public hunting areas 
collect sex and age data (paws for X rays) from shot squirrels 
and data on hunting pressure from the selected areas during the squirrel season. 
Responses of Prairie Chickens to Habitat Manipulation 
R. L. Westemeier, 
D. R. Vance 
,.. n , r nd a c q u« s »t ion and management for prairie chickens began near Bogota in 
Fo!ndation"of n, 6 J h ® purchase of 77 acres by the Prairie Chicken 
!??! S \ Subsec l uent acquisitions, mainly by the Prairie Grouse 
toT 000 acL h 1 ’'? 0 ,S D Cah P^r-The Nature Conservancy, increased the acreage 
1,000 acres by 1973- Population responses at Bogota during this period were 
?or 3 decline f ° r 2 years 0963-64) ; (2) restive stability 
th . ? 0965-67); (3) encouraging increases for 5 years ( 1968 - 72 ); and 
surre«;<; C f) ineS years (1973-74). The average population change and hatch 
trends in U th^ 9 fl h \ fOUr per,ods are shown in Table 2. Thus, the four major 
ds in the flock at Bogota are well correlated with the success of the hatch 
analvsis P f 6 °I h 5 3 f ° Und ° V6r the 12 ” year P eriod - Also, a linear correlation 
vears rLSLd^ annua * po P u,ation changes versus the hatch success for the 12 
years revealed a significant correlation (r = O. 556 , P^0.05). 
r n '1!?'*°** in ? reasin 9'V evident that success of the hatch must be at least 
h , P h or a population of greater prairie chickens to remain stable. Actually, 
less than C M S Jr r e Tf S fo ™ d ° nly on 5anct nary land averaged 67 percent and not 
'**?'*" I !° r the l0 ' year peri ° d ’ *963-72. The primary limiting factor 
snr!nr J * P ° pulatlon appears to have shifted from poor nest success due to 
P , ? P*owmg on private land and to inadequate nest habitat, 1 963 - 68 , to poor 
hatch i‘n C to 7 C dUe t0 pre . datlon on sanctuary land, 1973-75- Since the success of the 
Sation wi ca 5 nnoJ he n r (MWRL l8(8 > :3 >' primarily due to mammalian pre- 
of 076 .ncrel- ? P !"" ,St ! c about the population level at Bogota in the spring 
harasLenr nna ? 9 lnteractl0ns batween pheasants and prairie chickens and ? 
addition*? ne5 t Parasitism by pheasants (MWRL 18(6):2-3) have recently become 
Ilf to?s 8 ° rS -l e opardizing efforts to preserve prairie chickens in 
