
175 
Table 4. -- (continued) 
South Dakota 

Transect No. Ducks per sq. mile Water areas per sq. mile 
ET 
1 ll.l 7.4 
2 7.5 4.7 
3 5.6 3.4 
4 3.1 32.5 
Average 6.4 4.7 
Table 5. -- Breeding population indices for North Dakota and South Dakota 

a Total Number Ducks 
‘State Total square miles Uncorrected Corrected * 



North Dakota 70, 665 1, 349, 700 1, 799, 600 
South Dakota 77, 047 493,100 657, 470 
Total 147, 712 1, 842, 800 2,457,070 
* Computed on assumption only 75 percent of birds observed. 
Allowing for a minus 25 percent error, the corrected number of ducks per 
square mile for North Dakota would be 25. 5; for South Dakota, 8.5. This would 
indicate that North Dakota had almost three times as many ducks and 2.7 tirnes as 
many water areas as South Dakota. The number of ducks per water area in North 
Dakota was 1.5; South Dakota, 1.4. 
As usual, there is only a rough correlation between number of water areas 
and number of ducks. Water, of course, is basic to waterfowl distribution and yet 
other factors obviously are present. Itis quite possible that water distribution the 
previous July might correlate more closely with the spring breeding population. 
Summary 
Nine transects which had been in use since 1946 in Nebraska and the Dakotas 
were again flown in 1950. The findings indicated a significant increase in water areas 
but also a decrease in ducks per square mile. The recorded decrease in ducks on these 
established transects was likely occasioned to some extent by both the timing of the 
inventory in relation to the migration and the greater availability of water areas in 
those sections of the States not covered by the transects and which normally are not 
considered attractive breeding habitat. 
The older transects thus did not adequately reflect conditions outside of the 
better sections in this year of water abundance. While it was felt that in most years 
these transects would provide satisfactory indices, it was, nevertheless, considered 
desirable to establish new transects which would be more reliable under varying 
conditions caused by. seasonal differences in water distribution and weather. State-wide 
transects were, therefore, undertaken and will provide data which can be used for 
comparison in future years. 
