MONTHLY WILDLIFE RESEARCH LETTER 
Vol. 1, No. 11 
Page 2 
R. D. Lord 
W-h2-R-8 
Annual census drives were carried out on the study areas at Robert 
Allerton Park this year with the aid of the University’s class in wildlife 
management. Of 56 rabbits seen on the U-H area, 2h had yellow tails. Because 
133 rabbits had been trapped, had their tails dyed yellow, and released, the 
population prior to the hunting season was calculated to have been 310 rabbits 
on this 100-acre area. The estimated population was 259 rabbits in 1957 and 
333 in 1956. 
Of 62 rabbits seen during the drive on the sanctuary area, 15 had 
yellow tails. Because 29 rabbits had been trapped, dyed, and released on this 
area, the rabbit population was calculated to have been 120 rabbits. The 
estimate is probably correct because the catch per unit effort (rabbits per 
trip-night) also was down (to 25 per cent). This is low compared with the 
estimate of 238 rabbits on the area last year. The study was not in operation 
on this area in 1956. 
The November spotlight-roadside census at Sibley gave the highest 
figure obtained in 22 censuses over 18 months. In 73 miles of census route, 
lli9 rabbits were seen: 2.Oh rabbits per mile. The nearest approach to this 
was in December of last year when 1.67 rabbits per mile were seen on the same 
census route. The most meaningful comparison is with the data from November of 
last year when 1.10 rabbits were seen per mile. 
W-55-R-3 F. Bellrose 
During November, extensive aerial waterfowl censuses were made on 
four occasions: the 6th, 12th, 19th, and 28th. Two other local censuses were 
made on November 15 and 21 in the central part of the Illinois River valley. 
Waterfowl populations during this period were far below normal, as 
shown by the data below: 
Period 
Illinois 
1958 
River 
19hh-1958 
Mississippi 
1958 
River 
1916-1958 
November 1-7 
U52,000 
683,000 
167,000 
268,000 
November 8-lh 
562,000 
1,159,000 
192,000 
h11,000 
November 15-21 
701,000 
1,14*0,000 
332,000 
365,000 
November 22-28 
601,680 
1,295,000 
1*55,710 
506,000 
The large decrease in the number of ducks in Illinois was most apparent 
in the populations of lesser scaup, ring-necked duck, canvasback, and mallard. 
