- 3 - 
week of October, which indicated a prolonged nesting season. 
The high prehunt populations on the areas in 1967 resulted from increases in 
the numbers of fall coveys, with slight increases in mean covey sizes. In 1966 , 
20 coveys were located on Dale, with 16.4 birds per covey; and 19 coveys were found 
on Forbes, with 16.5 birds per covey. In 1967, 23 coveys on Dale averaged 1 7.3 
birds per covey, and 31 coveys on Forbes averaged 16.6 birds per covey. 
5- Responses of Prairie Chickens to Habitat Manipulation R. L. Westemeier 
The annual search for prairie chicken nests on the Bogota Study Area has 
usually been conducted after the main period of hatch. Thus, physical characteris¬ 
tics of nest sites, such as height of cover, are noted at a time when cover height 
maybe of minimal importance to nesting hens. Because prairie chickens nest relatively 
early and have only limited renesting capabilities, residual vegetation from the 
preceding growing season is vitally important as nest material. The height of cover 
at the period of nest initiation can therefore be estimated during early April by 
noting the height of residual vegetation in fields scheduled for searching later in 
the summer. Cover height is defined as the prominent horizontal plane formed by the 
tops of vegetation when viewed at a low angle. 
The mean height of the cover at the sites of 60 prairie chicken nests was 
22+10 (SD) inches with a range of J to 48 inches at the time the nests were found 
during the period 1963-67 at Bogota. At the period of nest initiation (early April), 
however, the mean height of cover for a sample of 31 nests was only 11+5 (SD) 
inches with a range of 3 to 24 inches. 
Redtop fields combined to a height of 10 to 16 inches have been the primary 
cover type available for nesting on the Bogota Study Area in recent years. Thus, 
nesting hens readily accept relatively short cover in which to establish their 
nests, but this does not preclude the possibility that taller, undisturbed stands 
of grass are not also acceptable for nesting. 
Rabbit Management J. a. Bailey, J. C. Hanson 
Trapping of cottontails on the Allerton Park 4-H Area during October and 
November, 1 967 ^ resulted in the color-marking of 76 rabbits. On November 18, 
Dr. H. H. Shoemaker and wildlife management students of the University of Illinois 
cooperated in the annual autumn census. Compared with numbers of rabbits seen in 
previous years, few rabbits were seen during this year's coordinated drives of the 
120-acre study area. There were 145 observations of rabbits, 94 of marked animals 
and 51 of unmarked animals. It was therefore estimated that 65 percent of the 
population had been color-marked. 
Using the Petersen-Lincoln Index, the estimated number of rabbits on the 4-H 
Area during mid-October, I9&7> was 117 + 14. During 1956-61, estimates of the 
numbers of cottontails on the 4-H Area during autumn ranged between 2 and 3 rabbits 
per acre. However, the population declined abruptly in 1962 and autumn population 
estimates have varied between 0.8 and 1.5 rabbits per acre during 1 962 - 67 . This 
decline has, at least in part, been due to deteriorating habitat conditions caused 
by plant succession and a tree-planting program. 
