1950-1951, since both winters were mild compared to those when 

 Schwartz made his study. The operation of the upper threshold of 

 light and temperature is indicated by the latest observed booming- 

 ground activity on June 12, 1951, which was a cloudy, cool day. As 

 late as May 30, 1951, spirited booming-ground activities and indica- 

 tions that hens were present on the booming ground were noted. 



Summer Activities of Males 



In summer, during the molt, males seldom are seen, and they 

 are reluctant to fly when disturbed. Adults of both sexes were ob- 

 served in low areas where shrubs and associated tall grasses pro- 

 vided favored loafing cover. No evidence was found that the few 

 upland trees were used as loafing cover by adults in summer. 



Reproductive Cycle of Females 



In winter, too few females were observed to justify drawing 

 definite conclusions as to their activities then. The greater prairie 

 chicken was seen in many places other than the Welda Area, and 

 in all instances males predominated or no females were seen. It 

 seems that the daily routine of females involves fewer conspicuous 

 movements by flight than does that of males. 



Although no intensive study of the behavior of females in the 

 breeding season was attempted, such observations as were made 

 merit the same conclusions as those drawn by Schwartz (1945:51). 

 In his discussion of the spring booming-season he concludes, "Dur- 

 ing the early part of the season the principal activities on the 

 booming ground are territorial disputes and booming. No females 

 are seen there until late in March, when an occasional hen visits 

 the booming ground for a short time. . . . These infrequent 

 visits may continue for a week or more; then suddenly the num- 

 ber of hens visiting on a booming ground increases to a rather 

 constant maximum, marking for several days or a week the so-called 

 height of the season. . . . After this period the number of hens 

 decreases very rapidly to a few who come in only occasionally." 



In this study, the earliest observation of a female on a booming 

 ground was on February 25, 1951. The peak of mating, in 1950, 

 occurred in the second week in April. In 1951, although seven 

 mornings were spent observing booming-ground activity from a 

 blind between March 24 and April 25, no peak of mating activity 

 was observed. The largest number of females observed in any one 

 morning, in 1951, was three on April 13. 



Hamerstrom (1939:112) concluded that most of the nests of the 

 greater prairie chicken in Wisconsin were begun at the height of 



[23] 



