Vo 1. 14, No. 7 
Page 3 
5. Responses of Prairie Chickens to Habi tat Manipulat ion R. L. V/estemeier, 
D. R. Vance 
t leather is one of many factors that can affect reproductive success of 
prairie chickens. After a relatively dry fall and winter, precipitation in 
east southeastern Illinois in March, April, and May I97I amounted to only 
6.6 inches, in contrast to the norm of 11.7 inches (data from the Illinois 
Cooperative Crop Reporting Service). During April, an important period for 
the initiation of prairie chicken nests, precipitation amounted to only 0.9 
inch—2.9 inches short of normal. Drought conditions were even more pro¬ 
nounced on the Bogota Study Area. 
The basic effect of the dry spring was to promote early and complete 
tillage of cropland for spring planting of corn and soybeans. The early 
tillage resulted in little choice of nesting cover for prairie chickens 
other than the sanctuaries and the acres diverted from crop production 
through the Federal Feed Grain Program. No nests were reportedly destroyed 
by tillage operations at Bogota this spring. Whi1e the early tillage and 
the resultant lack of nest destruction were beneficial to prairie chickens, 
the drought conditions delayed the phenology of vegetation on the sanctuaries. 
The retarded growth of the vegetation on the sanctuaries, coupled with the 
lack of weedy grain stubble on private farmland, caused spring feeding 
conditions to be poor for prairie chicken hens at a time when the physiological 
demands of egg laying and incubation were critical. During the period 1963-70 
at Bogota, the clutch size of 38 prairie chicken nests averaged 12.2 eggs. 
Annual means ranged from 10.7 to l3.0 eggs. On the basis of 25 completed 
clutches found so far at Bogota this summer, clutch size has averaged 10.3 
eggs. This noticeable reduction in clutch size may be a function of the 
drought and the poor feeding conditions present this spring. 
D. R. Vance joined this project as Assistant Project Leader effective 
July 1, 1971. 
6. Rabbit Management G. B. Rose 
Energy consumption per day (MWRL 13(2):4-5) and growth of adult cotton¬ 
tail rabbits were measured during the period from April through August 1970 
and from April through July 1971* The amount of commercial rabbit chow 
consumed per day per rabbit averaged 57 grams for the rabbits in outdoor 
cages and 96 grams for those in outdoor pens, or 227 kcal per day for the 
rabbits in cages and 383 kcal per day for those in pens. 
Growth per day, for the penned cottontails, averaged 1.53 grams or an 
estimated 2.64 kcal/day, and ranged from 0.003 to 6.01 kcal. The proportion 
of the energy consumed that was converted into growth averaged O.69 percent 
(range, 0.00 to 1.40 percent), while the proportion of the estimated assimi¬ 
lated energy converted into growth, the net growth-efficiency, was 1.13 
percent (range, 0.00 to 2.29 percent). 
