that the major use of permanent cattail potholes was as nesting cover which is 
apparently not a critical item, while they were of purely secondary value for both 
territorial sites and brood rearing, presumably owing to their dense cattail margins. 
It appears that protection from grazing which would allow sedge-whitetop margins to 
develop might improve their qualities as territorial waters. This would also be 
applicable in regions where potholes suitable for brood rearing were scarce. 
A few additional small temporary areas could be created by placing small dams 
across waterways, but this would be at the expense of potholes already existing at 
the ends of these waterways. 
The development of sedge-whitetop eover in dennded areas by complete or partial 
protection from grazing might be benficial. The application of this measure should 
be guided by further study of the requirements of the breeding population and of the 
ecology of cattail and bulrush. 
The present high productivity of the study area is undoubtedly due to its 
climate, physiography, and chance application of the management practices discussed. 
Climate and glacial action produced an abundance of potholes of varying size, some 
of considerable permanence, lying in an area of relatively good soil, while the 
diversified land use brought about by small farming units has undoubtedly created 
the close interspersion of various cover types discussed in the introductory 
section. These factors combined to produce a nearly ideal balance of types. Farm- 
ing operations have not become so intensified and grazing is not generally so severe 
in this area as to cause a serious general reduction in upland nesting cover, 
Inasmuch as pressure on breeding habitat is increasing with the increase in 
hunting, while the available areas are diminishing with the expansion of agricul- 
ture, it seems desirable that programs for management be set up as rapidly as 
possible, even though we may not know the final answers to many questions, It is 
felt that trained observers, bearing the above concepts in mind and using aerial 
photographs. 
X. SUMMARY 
1. The potholes on the study area have been classified according to permanency 
and vegetation in order that their use by waterfowl might be correlated with described 
types. 
2. The factors influencing pothole types have been discussed and a postulated 
plant succession in the potholes of the region has been outlined. 
3. By means of marking the young, it was found that same broods moved overland 
considerable distances and made use of more than one pothole. 
Lh. By analysis of the periods broods resided in potholes, it was possible to 
determine the relative mobility of species. Pintail broods were the most mobile, 
followed in order by canvasback, mallard, redhead, blue-winged teal, and baldpate, 
while ruddy-duck broods were the least mobile. No motherless broods of any species 
were known to travel overland, 
5. By analysis of the movements of the brood population as a whole, it was 
determined that movements of canvasback, redhead, mallard, and pintail extended 
beyond the limits of the study area thus influencing the measurement of their 
populations. 
