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Vol. 4, No. 1 
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For analysis, the number of rabbits seen per mile was compared to the 
number of 10-foot contour interval lines intersected by that same mile on a 
geological survey map. The data plotted a positive regression by the method of 
least squares (m = 2.50) of rabbits seen with the number of contour lines inter¬ 
sected. The correlation coefficient was 0.71, which was significant by the t 
test at the 1 per cent level. Construction of a map showing the relative dis¬ 
tribution of the rabbits and the location of the moraines did not show any 
striking restriction of rabbits to the moraine system. It was apparent that 
cottontails were everywhere but we were looking for some relationship between 
the land and the relative abundance of rabbits. Because of the results of the 
statistical analysis, the river system was also drawn into the map and immediately 
the relationship became apparent. Wherever there were many rabbits there was 
either a moraine or a stream. Probably the dissection of the land by the stream 
and its tributaries over the past geological history has caused the necessary 
hillyness which is in some way more favorable to rabbits than the flatter land. 
W-55-R-5 F. C. Bellrose 
As part of the nation-wide January inventory of waterfowl, we made aerial 
censuses of waterfowl on the Illinois River between Grafton and Joliet and on the 
Mississippi River from Alton to Rock Island on January 8 and 9, 1961. In addition, 
waterfowl on Lakes Decatur and Springfield were also inventoried. 
Including the surveys of other observers in Illinois, we found 327,COO 
mallards, 16,000 black ducks, 2,600 canvasbacks, 2,000 lesser scaups, 11,000 
common goldeneyes, and 19,500 American mergansers. Including species which were 
low in number and species which were unidentified, 384,000 ducks were estimated 
to have been in the state. Last year's winter inventory provided the basis for 
an estimate of 543,000 ducks in the state at that time. Unseasonably cold 
weather in December combined with snow to result in the low number of ducks 
found on this year's inventory. 
W-56-R-5 G. C. Sanderson 
Compilation of data collected in Illinois from 1955 through October 1956 
shows that some wild, adult, male raccoons are sexually active (based on presence 
of sperm in the epididymis) by October, and, by December 97 per cent (113 of 116) 
of the adult males reach this stage. Most remain sexually active through April, 
but from June through September a majority of the adult males are sexually 
inactive. Average weights of testes indicate these organs reach maximum size in 
December. This size is maintained through January, but by the time most mating 
occurs (mating season is January 15 - April 15 with the peak occurring about 
February 15) the testes are already regressing in size. This regression continues 
