Vol . 8, No. 2 
Page 4 
results of the prebreeding census and the estimate based on the recovery of marked 
birds in the harvest was probably due to the high mobility of bobwhites in summer. 
The prebreeding census in March, completed within a few days, was conducted during 
a period of the year when mobility of bobwhites is minimal. The 2-month trapping 
period, however, occurred at a time of year when mobility of bobwhite cocks is 
probably at a peak. Movement data show that cock quail traveled distances as great 
as 3-2 miles during the summer of 1964, which suggests that the size of the breeding 
population on Forbes may be greatly influenced by immigration of quail from adjacent 
habitat onto the area. Also, intensive and extended use of the cock-and-hen trap¬ 
ping technique on an area, as on Forbes, could conceivably inflate the population of 
adult cocks by attracting cocks from adjacent habitat to hens used as bait in the 
traps. 
Table 3- Estimates of prehunt (November) quail populations on two census areas. 
area 
Estimate Basis 
Number of 
Qua j 1 
Percent Change from 
Prebreeding Census 
Qua i 1 per 
100 Acres 
1963 
1964 
1964 
1963 
1964 
FORBES 
Prehunt Census 
Harvest + 
349 
268 
+ 129 
23.2 
14.2 
Posthunt Census 
372 
400 
+242 
24.7 
21 .2 
Tag Recoveries 
3601134 
6201133 
+430 
23.9 
32.9 
DALE 
Prehunt Census 
Harvest + 
297 
286 
+522 
40.1 
26.5 
Posthunt Census 
263 
346 
+652 
35-5 
32.0 
5* Responses of Prairie Chickens to Hab ? tat Manipulation R. J. Ellis 
It is certain that if prairie chickens are to be preserved in Illinois, nesting 
refuges must be provided very soon (Monthly Wildlife Research Letter, December, 
1964). Because refuges are often expensive to acquire and maintain, it is important 
to know how large a refuge system must be to insure survival of one flock. 
Any prairie chicken preservation program in Illinois probably should aim to 
maintain no fewer than 500 prairie chickens in the fall population on each refuge 
system. Smaller populations probably would decline to precariously low numbers in 
years of extreme weather conditions. 
It is estimated that approximately 500 acres of good nesting cover are required 
in southern Illinois to maintain a prairie chicken flock numbering 500 in the fall. 
This estimate is based on the average of data collected at Bogota in 1 96 3 and 1964 
(Ellis 1964, Ellis I 965 ). It assumes a hatching success of 73 percent of the nests, 
10.2 hatched eggs per successful nest, a 40 percent survival of young, and a fall 
age ratio of 3 juveniles per 2 adults. It also assumes a rate of nest establishment 
