declined since 1963* In 1967 , only two nests were found on each sanctuary and 
chick production amounted to only 21 young for the 97 acres. Thus, only 10-3 
percent of the 39 nests and 8.9 percent of the 237 chicks produced on these tracts 
in the past five summers occurred in 19 ^ 7 * 
The prairie chicken population at Bogota was 42.3 percent smaller in I 967 
than in 1 963 - However, more hens have been seen on the two major booming grounds 
in the section containing the Yeatter and McGraw sanctuaries in the combined 
years of 1966 and 1 96 7 than in 19&3> 1964, and 1965 combined. For example, in 
1966 and 1967> 15 and 8 individual hens, respectively, were observed on the boom¬ 
ing ground on the Yeatter Sanctuary, yet only four and two nests, respectively, 
were found on this tract. 
The declining use of the older sanctuaries may in part be due to dispersion 
of hens to newly created nesting cover. One case is the 60-acre Donnelley 
Sanctuary with its 2nd-year stand of redtop which contained three nests in J967> 
two of which hatched and produced 25 chicks. 
6. Rabbit Management J. A. Bailey, J.^ C. Hanson 
A method, using weight and a measure of body length, for evaluating the 
physical conditions of cottontails has been described (Monthly Wildlife Research 
Letter 10(7):3)» This method provides condition indices which are used in com¬ 
paring weights of rabbits from different length- and age-classes. Condition 
indices for rabbits captured during monthly trapping periods on the A1 lertor. Park 
4-H Area ware used to evaluate trends in the physical conditions of cottontails 
during the periods of November through March in 1964-65 and 1 965 - 66 . 
Average condition indices for rabbits on the 4-H Area increased during 
November through early January and declined during late January through February 
in both 1964-65 and 1965 - 66 . In 1965* the average condition index continued to 
decline between February and March, whereas in 1966 the average index increased 
between February and March. These month-to-month trends in condition indices 
of rabbits in the 4-H Area accurately reflected month-to-month changes in the 
weights of rabbits that were captured in successive months on the area. 
Loss of weight by cottontail rabbits during winter has been reported by 
biologists in Wisconsin, Michigan, and Illinois. Biologists in Illinois were 
unable to prevent these weight losses by providing the rabbits with supplemental 
food. The above reports and the present data suggest that weight losses during 
winter are normal among cottontails in northern latitudes. Since most rabbits on 
the 4-H Area gained weight during November through early January and lost weight 
thereafter, it could be that winter weight losses by cottontails are caused by 
normal physiological changes triggered by the change in photoperiod at the winter 
solstice. 
