
Most of the potholes drained under the present program were temporary 
and of rather small size. The statement is often made that such drainage 
"improves the pothole into which the ditch runs. Although this may some- 
times be true in other areas, no evidence of it has been found at Waubay. 
In general, the relatively small volume of water drained has had little effect 
on the larger, deeper basins that received it, while the area of water and the 
number of potholes available during the nesting season have been reduced. 
Drainage since 1945 has reduced the original number of potholes on the 
study area by 9 percent and the original acreage by 3 percent. This is 
slightly less than the reduction in number of potholes of roughly 10 percent 
from 1945 to 1950 in the three-state area of the Dakotas and Minnesota reported 
in Nord et al. (1951). 
Effect on brood habitat 
Rearing potholes on the study area and in the surrounding country have 
been ample to supply the needs of the broods produced throughout the four 
years of the study. Even in 1950, the driest year, there was no evidence 
that broods were forced to use unsuitable habitat or to become excessively 
crowded into the better areas. The ability of the broods to move overland 
enabled them to make full use of the most favorable areas, and there is no 
indication that possible "improvement" of additional areas could have had any 
beneficial effect. 
Effect on nesting cover 
Since the drainage program is eliminating many potholes of the marsh type 
which contain the most abundant emergent vegetation, over-water nesting habitat 
is being reduced. While there is no evidence that the reduction that had al- 
ready taken place has had a harmful effect, there is no question but that its 
continuance can become harmful. 
The same statements may be made with regard to the dryland nesting cover 
furnished by the bottoms of those potholes which dry up before the nesting 
season. 
Effect on habitat for breeding pairs 
Since all types of water areas are used by breeding pairs, drainage of 
any water is harmful to this phase of the breeding cycle. The drainage of a 
large "brood area” in a region where such areas are abundant may not be harm- 
ful during the brood season, but such areas are also used by breeding pairs in 
the spring. An increase in carrying capacity would necessitate breaking up 
the larger areas into small units, rather than the reverse, as is being done. 
Bach pothole drained necessitates either a further concentration of the breed- 
ing population with a probable resulting decrease in productivity, or a re- » 
duction in the size of the breeding population. Stoudt (1950, 1951, 1952), in 
discussing trends in breeding population for South Dakota in 1950, 1951, and 
1952, concludes that breeding population will be reduced. This is borne out 
by figure 23 which shows the relation between numbers of water areas available 
51 
