Vol. 10, No. 4 
Page 3 
and 65 a decline of 35 percent was recorded and between 1 963 and 1964 a decline 
of 17 percent, occurred. These data show that the 2 earlier years of moderate to 
drastic losses have been succeeded by 2 years of static or slightly increased 
breeding populations. 
Also encouraging is that during the 1967 breeding period, booming activities 
were observed in 8 Sections (square miles) as compared with only 3 Sections in 
1966. Most of the dispersion of birds in 1967 was in marked response to the newly 
available nesting habitat made possible through the efforts of (I) the Prairie 
Chicken Foundation of Illinois, (2) the Prairie Grouse Committee, Illinois Chapter- 
The Nature Conservancy, and (3) cooperative leasing arrangements between the 
Illinois Department of Conservation and local farmers. 
Prairie chicken hens began appearing on the booming grounds on March 7, 1 967 -- 
about 9 days earlier than in 1966 and also earlier than in any of the years 1963 - 
65* The peak number of hens on the booming grounds was approximately 1 week 
earlier in I 967 (April 1) than in previous years, and the first successful 
copulation, as noted by observers in blinds on the booming grounds, occurred on 
March 25* somewhat earlier than in previous years. 
6 . Mbb.it jjana gement j. A . Bailey, J. C. Hanson 
Evidence for the occurrence of regionwide and synchronous fluctuations in 
the abundance of cottontail rabbits was available at least as early as 1928 . 
However, very few states had obtained systematically collected data on the abundance 
of cottontails before 1945. Since 1950, many states have conducted annual censuses 
of the abundance of cottontails. These data were solicited and obtained from 10 
states: Minnesota, Wisconsin, Michigan, New York, Iowa, Illinois, Indiana, Ohio, 
Missouri, and Kentucky. 
A statistical analysis of the census da^a obtained from the 10 states has 
demonstrated the occurrence of regionwide and synchronous fluctuations in rabbit 
abundance during 1950 through I 965 . During this period, cottontai1-populat ion 
indices were below average in 1951 , 1952, and 1953 * for every state that provided 
data. Contrariwise, nearly alI of these states had above-average indices to 
cottontail abundance during 1956, 1957 * and 1958; and again had below-average 
indices during 1 96 1 through 1964. 
Regionwide and synchronous fluctuations in the abundance of animals have been 
reported for other species, particularly those which are involved in the so-called 
10-year cycle of game abundance in northern latitudes. The cause or causes of the 
10-year cycle have not been detected, although its existence has been documented 
since 1911. It is therefore not surprising that the existence of regionwide, 
synchronous fluctuations in the abundance of cottontails is also unexplained. 
