MONTHLY WILDLIFE RESEARCH LETTER 
Department of Conservation and Natural History Survey, Cooperating 
T. G. Scott, Editor 
Urbana, Illinois 
March 1958 
Vol. 1, No. 3 
W-30-R-11 W. R. Hanson, R. F. Labisky 
Breeding activity among pheasants on the Siblejr area was somewhat 
retarded during early March but progressed rapidly during the latter portion 
of the month. Because photoperiod is important in triggering sexual activity 
in birds, the unusually low amount of sunlight (or extended periods of cloudi¬ 
ness) characteristic of early March probably caused the lag in the breeding 
cycle. Social interactions among and between the sexes were common; adult 
pheasants were more aggressive breeders than juveniles. The behavior of adult 
cocks was indicative of territory establishment during late March; harem for¬ 
mation was not evident. 
Crowing counts on the Sibley area reached a frequency of 23.9 cock 
calls per 2-minute period in late March; comparable counts for 1957 showed a 
frequency of only 10.9 calls per 2-minute period. The increased frequency 
of cock calls in 1958 mainly reflects the increased numbers of cocks in 1958. 
W-U2-R-7 R. D. Lord 
Data from the 1957-58 season on the population dynamics of rabbits 
on the two 100-acre study areas at Allerton Park which are being investigated 
to determine the role of hunting in the annual turnover were analyzed. One 
area is hunted and the hunters are closely checked. The other area is a wild¬ 
life sanctuary and is not hunted. 
The productivity of rabbits on the hunted area proved to be somewhat 
greater than that of the unhunted area in spite of a smaller spring population. 
The population in fall was 2.6 rabbits per acre on the hunted area and 2.U 
rabbits per acre on the sanctuary. 
By late winter, the population on the hunted area had dropped to 0.3 
rabbits per acre and on the sanctuary to 0.6 rabbits per acre. The winter 
mortality on the hunted area was 88 per cent of the fall population and less 
than 75 per cent on the sanctuary. 
NATURAL 
HISTORY SURVEY 
r\ n 
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