MONTHLY V/IIDUFE RESEARCH LETTER 
VoL. 2, Ho. I 
Phge 2 
for 1957, without the neens of determining the ege of the rabbits to the month, 
imiicated Pt to 27 per cent of the annual crop resulted from juvenile breeding. 
A paper on the new disease of cottontails previously reported was 
piven at the annual meeting of the Illinois Academy of Science. 
W-55-R-3 P. Bellroee 
Three aerial censuses were taken of waterfowl populations in the Missis- 
sii»pi , Rock, and Illinois River valleys during April. This completes the aerial 
waterfowl censuses for the spring season. 
Flooding of agricultural lands along the Hock River resulted in many 
thousands of ducks stopping in that area during early April* A late northward 
flight of mallards appeared on the lower Mississippi River on April 9, as rising 
waters flooded bottomland com fields. However, during the month there was a 
general decline of waterfowl, so that by April 23, only 11,000 ducks were found 
on major woter areas in the state. 
W-56-R-3 
0. Sanderson, K. Johnson 
Natural cavities suitable for wood-duck nesting In the Havana study 
area were Inspected at weekly intervals in order to determine nesting activity* 
Twenty-six wood-duck nests were found in then. Hens ere incubating or still 
laying in 20 of these nests; 1 has been deserted) 5 have been destroyed, 3 by 
raccoons and 2 by squirrels. 
Sick and deed raccoons have been obtained for autopsy from time to 
time since August 1956. Approximately half of these animals had lead in their 
livers. During the late fall and early winter of 1956 it became apparent that 
most raccoons found sick or dead had varying conoantrations of lead in their 
livers. In order to learn more about the lncidenoe and meaning of lead in 
raccoons, livers were collected from 100 raccoons killed by hunters end trappers 
during the 1953-59 season. The ye were mostly collected at fur buying stations 
in Piatt and Fulton counties. Ninety-nine of the 100 were found to contain 
lead, ranging from 2 to 32 micrograms per gram of liver. Thirty-seven of the 
100 had fi micrograms and only 10 animals had more then 10 mlcrograme. The 
average amount was 7 microgrems. 
These animals apparently were healthy and were normal so fsr as woent 
of body fat was concerned. Condition factors were calculated for these animals 
and those with more than 10 micrograms of lead per gras of liver were in Just 
as ^ood physical condition as those with 10 mlerograns or less* The ratio of 
adrenal weight to body weight did not indicate that the animals with higher lead 
concentrations were under stress any more than those with low concentrations* 
Thus it does not seem that these amounts of lead alone are enough to cause the 
death of the raccoons* 
