Vol. 7, No. 9 
Page 4 
5. Responses of Prairie Chickens to Habitat Manipulation R. J. Ellis 
Twenty-one prairie chicken broods were reported or observed on the Bogota 
Study Area during the summer of 1964. Counts or reasonable estimates of the number 
of young per brood were available for 13 broods. Estimates of the size of the 
young were available for 16 broods. The ages of the young whose approximate size 
was known were estimated using the method of Baker (1953: pis. 2 and 3) and 
unpublished data of Stan Etter (personal communication). 
Prairie chicken broods observed on the Bogota Study Area during 1964 were 
smaller than those observed in 1963 (Table 2), a condition probably related to 
decreased fertility of eggs. In 1964, the fertility of 101 eggs was 92 percent; 
in 1963, the fertility of 116 eggs was 97 percent. The lower fertility of eggs 
in 1964 seemed to be associated with the wet spring. One nest was found in which 
all eggs became infertile due to flooding. Some infertility of eggs found in 
successful nests may have been due to excessive moisture. 
The mowing of a 20-acre clover field adjacent to the 77-acre Yeatter Prairie 
Chicken Sanctuary No. 1 on June 8, 1964, further reduced brood sizes. The mower 
operator reported encountering five broods as he mowed. Two small young killed by 
the mower were accidentally found. Probably other dead also were in the field. 
This incident demonstrates that hayfields adjacent to good nesting cover may be 
detrimental to prairie chickens if small broods are present at the time of mowing. 
May 22 was the estimated mean date of hatching of 16 prairie chicken broods 
on the Bogota Study Area during 1964. This date was 10 days earlier than the mean 
date of hatching of 14 broods on the same area during 1963- The difference in 
hatching dates between the 2 years could be related to climatic differences or to 
errors in aging broods. 
Table 2. Numbers of young in prairie chicken broods, Bogota Study Area, 1964. 
Numbers in parentheses are sample sizes. 
Estimated Age 
of Young in 
Weeks 
Average Number 
of Young per Brood 
1963 
1964 
4 
9-0(4) 
8.5(2) 
5 
9-0(3) 
5-3(3) 
6 
— (0) 
5-3(6) 
7 
6.0(1) 
5-5(2) 
8 
6.5(2) 
— (0) 
Average 
8.2(10) 
5-8(13) 
Baker, M. F. 1953- Prairie chickens of Kansas. Univ. of Kansas Museum Nat. Hist, 
and State Biol. Survey Misc. Publ . 5- 68pp. 
