Vol. 4, Mo. 11 
Page 4 
peak of the migration, November 6-15, there were only 560,000 mallards in the two 
river valleys. Mallard numbers were especially low in the Illinois River valley 
south of Havana and in the Mississippi River valley south of Keokuk. 
The decline in mallard populations in this region of Illinois began in 1956, 
when peak numbers dropped to 1,485,000 from the 1955 high of 2,435,000. In 1957 
the populations increased to 1,706,000 and then decreased in 1958 to 1,166,000. 
The decrease continued in 1959 to 850,000. A slight increase occurred in 1960 
with populations of 1,064,000, but in 1961 the populations resumed their downward 
trend descending to the low of 560,000. 
7. Wildlife-Insecticide Relationships R. W. Lutz 
The South Sheldon area (9,338 acres) and the East Iroquois area (7,450 acres) 
were treated with 2 lbs. per acre of aldrin during the periods from October 27- 
November 6, and November 6-13, respectively. Questionnaires designed to provide 
information on mortality were distributed to the 33 farmsteads on the East Iroquois 
area. 
