6 . 
Waterfowl Inventory 
Vol. 4, No. 12 
Page 4 
F. C. Bellrose 
Only two waterfowl censuses were made in December as the fall migration was 
nearing its end. Aerial surveys of the Illinois and Mississippi River valleys 
were made on December 5 and 14. 
A few tardy autumn migrants, green-winged teals, widgeons, gadwalls, and ruddy 
ducks were still present in fair numbers on December 5. However, by December 14 
only those species that normally winter in Illinois were found. 
As late as December 13 it appeared that a small flight of mallards had arrived 
along with common goldeneyes, American mergansers, and bald eagles. At that time 
there were 413,000 mallards? 11,800 black ducks; 1,000 pintails; 5,400 goldeneyes; 
10,800 American mergansers; and 120 bald eagles in this region of the state. 
Of particular interest was the low number of goldeneyes on the Illinois River, 
500, as compared with the number on the Mississippi River, 4,900. Five years ago 
the numbers of goldeneyes on the two rivers were quite similar. The difference 
in populations seems attributable to the decline of mollusca in the Illinois River. 
Detergent pollution has affected the mollusca in the Illinois River to a much 
greater extent than that in the Mississippi River. 
7, Wildlife - Insecticide Relationships R, W. Lutz 
| The wildlife questionnaires distributed to farmers prior to the fall applica¬ 
tion of aldrin on the South Sheldon and East Iroquois areas were returned during 
December. The known wildlife mortality on these areas, table 3, is based on 54 
questionnaires (96.4 per cent return) from the South Sheldon area and 29 question¬ 
naires (85.3 per cent return) from the East Iroquois area. 
These data represent a minimum estimate of mortality. The reports of mortality 
were substantially greater on those farms where harvesting operations were still 
in progress, because farmers who had harvested their crops prior to the application 
of the insecticide spent little time looking for dead animals. 
Most mortality occurred during the first 2 weeks following treatment. Many 
songbird species had migrated prior to the application of the insecticide and 
were spared the heavy losses they suffered during spring applications. 
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