Vol. 2A, No. I 
Page 6 
recorded. From this information we will attempt to develop a suitable model for 
predicting herd size for the following season so that hunter quotas can be 
accurately set. Secondly, available data on harvest, reproduction, mortality, 
and similar information will be used in a simulation model to answer "what if" 
types of questions, such as what would happen if the number of hunters in a 
region substantially increased. Next month we will describe the techniques used 
in evaluating harvest data and the numerous biases encountered when using this 
type of data. 
Cooperative Waterfowl Research - W-38-R F. C. Bell rose, 
S. P. Havera, 
G. A. Perkins, 
H. K. Archer 
"Where are all the ducks?" was a question often asked by perplexed and 
frustrated duck hunters, researchers, and journalists during the 1980 waterfowl 
hunting season, one of the poorest in memory. Weekly aerial waterfowl censuses 
conducted by Robert Crompton from September through December revealed that the 
number of ducks in both the Illinois and the central Mississippi River (Grafton 
to Rock Island) valleys ran higher in 1930 than in 1979 until the 1st week of 
October. Then the normal fall buildup of birds in the valleys slowed until by 
the 3rd week of November there was only one-third as many birds in the Illinois 
Valley and one-half as many birds in the central Mississippi Valley as were 
observed during the same week of 1979* A similar trend was noted in the lower 
Mississippi Valley (Cairo to Grafton) and selected cooling lakes and reservoirs 
in central and southern Illinois. Totals for 3 biweekly censuses were only one- 
third of the 1979 numbers on comparable flights. 
Numbers of ducks in the Illinois Valley peaked at 1,256,000 during the 1st 
week of November in 1979* The 1330 peak of 5^^>000--a 57% decrease--came 
approximately a week earlier. For further comparison, our highest peak count in 
the Illinois Valley was 1,349,000 on 29 November 1978. The central Mississippi 
Valley peak numbers were 1,1*59,000 and 943,000 for 1979 and 1980, respectively— 
a decrease of 35%. A 70% decrease in peak population numbers from 326,000 in 
1979 to 99,000 in 1980 was documented for the lower Mississippi Valley and the 
selected lakes and reservoirs of central and southern Illinois. 
Contrary to duck populations, Illinois River valley Canada and snow goose 
populations peaked at higher levels in 1980 than in 1979* In the central 
Mississippi River valley, numbers of both species were down slightly in 1980 
from 1979. Population peaks are misleading in this case because counts for 
both species and both rivers were substantially lower each week after mid- 
October than for corresponding weeks of 1979. The biweekly censuses of the 
lower Mississippi Valley and scattered central and southern Illinois lakes 
revealed fewer geese throughout the 1980 season compared with 1979. 
Several factors caused the shortage of ducks during the past waterfowl 
season. Populations were lower because of a poor hatch of young on the breeding 
grounds. Also, abnormally heavy precipitation in the prairies of the Dakotas and 
Saskatchewan during late summer caused flooding which increased the availability 
of natural foods to ducks. These extra food resources, combined with relatively 
mild weather, held the birds farther north during our hunting season. We hope that 
the late summer precipitation on the breeding grounds will be conducive to a good 
hatch this spring so that more typical numbers of ducks will wing their way through 
next fall. 
