-3- 
; 
of the Dale Area, however, sustained a population loss of 66 percent during the 
same period. The prebreeding population on the burned zone in 1 968 was 500 percent 
higher than any other prebreeding population recorded on this zone since the late 
winter of 1964. If the size of the prebreeding population continues to determine 
the size of the subsequent prehunt population, a substantial increase in the prehunt 
population in I 968 would be expected on the burned zone. Thus , burning appears to 
be an effective and economica 1 tool in qua i 1 management . 
5- Responses of Prairie Chickens to Habitat Manipulation . R. L. Westemeier 
During the spring period of late March to mid-April, 1 968 , 19 areas in eight 
counties in south-central Illinois were systematically cruised in search of booming 
prairie chickens. Censuses were discontinued on four areas where no prairie chickens 
were found in the spring of 1967 . 
A total of 143 booming cocks were found on 13 of the 19 areas surveyed. In 
addition, a remnant flock near Hoyleton in Washington County, learned about in May 
1968, reportedly (by local residents) contained six cocks. Thus, by assuming a 
50.50 sex ratio, the known statewide population of prairie chickens numbers about 
300 birds in 14 flocks this spring. On comparable surveyed areas, there were 19 
percent fewer cocks this spring than the statewide count of 177 cocks found in 1967 . 
Decreases were recorded on 11 areas, 3 of which were totally defunct (the West 
Liberty and Shamrock areas in Jasper County and the Hookdale Area in Bond County). 
No change took place on three areas, one of which was the Hunt Area in Jasper 
County, where a single cock has been found for the past three springs. Increased 
population levels since 196 7 were noted on two areas: (1) near Loogootee; an area 
which overlaps Effingham and Fayette counties, and (2) near Fairman; an area which 
overlaps Marion and Clinton counties. 
The Bogota Area, the main management and research area, sustained the smallest 
decrease (-14 percent) among the areas on which declines were recorded, and 
continued to support the largest self-contained flock (37 cocks) of prairie chickens 
in Illinois. It is interesting that the birds on five areas either held their own 
or increased in number with little or no deliberate habitat management. 
6. Rabbit Management j. a. Bailey 
If information on food preferences and nutrition of wild cottontails is to 
find application in habitat management, there must be an awareness of seasonal 
variation in the availabilities and nutritional values of plant foods and also of 
the fact that young, growing animals have nutritional requirements differing from 
those of full-grown animals. 
The physiological condition of a plant, as determined by its stage of maturity, 
recent weather, soil conditions, and the maturity-delaying effects of mowing or 
grazing, influences its palatability and its content of digestible nutrients. Thus, 
foods that are preferred and nutritious at one stage of growth may be poor foods 
for cottontails at other stages, and food-habits studies must be related to this 
seasonal variation. 
Basal metabolic rate per unit of body weight is greater for small animals 
than for large animals and also greater for young animals than for mature animals. 
Young animals also require large amounts of energy for the processes of growth. 
Therefore, the energy requirements of young animals are considerably greater than 
