Bag check surveys 
Bag-check information on the Upper Mississippi Refuge hes 
been obtained by staff member field contacts with huntérs through- 
out the refuge. The checks are made at access points, where 
hunters concentrate, and in the field as well. These contacts 
were distributed throughout the refuge and throughout the season, 
to provide as representative a sample as possible. For purposes 
of comparison, the same areas have been checked each year. 
In the early work on Mark Twain Refuge, information was ob- 
tained by spot checks of hunters at access points or in the field, 
in a manner similar to that used on the Upper Mississippi. The 
same system is still used at the Keithsburg Unit. However, the 
State of Illinois now operates check stations at Quincy Bay south 
of the Gardner Unit and near the Batchtown and Calhoun Units, and 
the State of Iowa operates a check station near the Louisa Unit. 
Since the State checking stations were established, much of the 
bag-check information on these areas has come from these stations. 
The States of Illinois and Iowa have been very cooperative in 
making these data available. Throughout the Mark Twain Refuge, 
the staff continues to conduct spot checks of hunters to provide 
information from areas which are not covered by the State check- 
ing stations. We believe that reasonably good sampling results. 
Table 2 indicates the coverage obtained on the various units 
under study. The sampling percentage is derived by dividing the 
number of hunters checked into the estimated total days of hunt- 
ing in each area. Although the data for the Upper Mississippi 
Refuge indicate a sample of only 5.77% of the hunters using the 
refuge, it must be remembered that there are about three times 
as many days of hunting done there as on Mark Twain. 
Crippling loss data: 
Crippling loss data were obtained by questioning most hunters 
contacted in connection with bag check surveys. Therefore, these 
data represent voluntarily reported crippling losses and are 
generally believed to be minimum. 
Crippling-loss percentages were derived by adding reported 
cripples to checked kill to give the total kill, and then the 
crippling loss was calculated as a percentage of the total kill. 
Thus, if the average bag per day amounted to 1.10 ducks and the 
average crippling loss to 0.25 ducks per day, the total average 
kill per day was determined to be 1.35 ducks. Crippling loss was 
then determined by dividing 1.35 into 0.25 and converting the 
result to a percentage (18.5%). 
