MONTHLY WILDLIFE RESEARCH LETTER 
Vol. 2, No. 3 
Page 2 
The hunting pressure in terns of gun-hours was steadily increased 
during the 3 years of study. From the first to the second year there was a 
ii3 per cent increase, and this year there was a 26 per cent increase over last 
year. Yet in spite of considerable changes in the size of the preseason 
rabbit populations and the amount of hunting pressure, hunters seem consistently 
to harvest the same proportion of the fall population (about 3h per cent). 
Analysis of lens-aging data indicates that there is a greater survival 
rate of rabbits born in the beginning of the breeding season (March and April) 
and the end (September) than during the middle (May, June, July, and August), 
A sample of 56 rabbits taken this month showed a prevalence of 
pregnancy of 0,97 and a mean litter size of h.61. Both figures are virtually 
identical to those for March last year. 
W-55-R-3 F. Bellrose 
Five aerial censuses of x^aterfowl were taken in the Illinois and 
Mississippi valleys during the month. The chronology of the migration was 
ahead of that for the last two springs, and populations were larger than in 
1958 but below those of 1957. 
High water which flooded fields made for excellent feeding conditions 
this spring, probably accounting for the larger population than last spring 
when little flooding occurred. More ducks were found in the Mississippi River 
valley this March than in the Illinois River valley in contrast to last fall 
when the situation was reversed. 
W-56-R-3 G. Sanderson, K. Johnson 
A late-winter inspection of natural cavities on the areas for study 
of raccoon-wood duck relations has been completed. Of 90 cavities inspected, 
7 per cent were occupied. Raccoons were found in 10 cavities, barred owls in 
3, a flying squirrel in 1, and bees in 1. The band of Tanglefoot, placed 
last year, did not prevent raccoons from climbing the cavity trees during the 
winter season; Tanglefoot will have to be re-applied this spring to prevent 
raccoons from reaching the natural cavities. 
Two additional woodlots were inspected for natural cavities suitable 
for wood duck use. One wood-duck nest was located in a nest box. Egg laying 
began on March 18, 1958 and March 17, 1959. 
The indices to populations of raccoons based on hunter and trapper 
reports for the 1957-58 season were still at a high level even though for the 
two seasons just passed they were down somewhat from those of the previous few 
seasons. 
