6. Owing to the mobility of broods, allowing them to select suitable areas, 
it was possible to gain data on their preferences. It was found that their first 
preference was large open areas with sedge-whitetop margins, while similar areas 
with bulrush cover were a close second. 
7. It was found that movement was stimulated both by high or rising water 
levels and by rapidly falling water levels. 
8. Depth was found to be an important factor influencing the selection of 
potholes. During periods of low water, potholes more than 2 feet deep were defin- 
itely preferred to shallower areas. 
9. The abundance of potholes was found to have an effect on movement, and 
the most movement took place where potholes were closely spaced. 
10. Food appeared to be an unimportant factor in the selection of potholes. 
11. The presence of other broods or other waterfowl species did not appear to 
influence the use of areas by duck broods. 
12. Human intrusion was found to influence brood movement in some cases, but 
it often had little effect and some broods could not be driven from their potholes, 
13. It was found that as broods became older their mobility increased. 
1h. Brood mortality on the study area was lower than expected. The canvas- 
back and mallard, which made wp nearly half of the obervations, suffered no known 
losses of young. The loss during an average period of 25 days was roughly 10 per 
cent. Most of the birds lost were Class I. 
15. Diving-duck broods were found to disperse earlier than broods of river 
ducks. 
16. Young ducks in the wild appeared to require less time to reach flying age 
than the same species raised in captivity. 
17. The study area was found to support 88 breeding pairs per square mile 
which produced 50 broods per square mile (a success ratio of 0.56 broods per pair). 
' 18. Breeding-pair use was found to be greatly influenced by pothole size, 
River-duck pairs showed greatest per acre use of areas 0.0 to 0.5 acres in size. 
Diving ducks preferred areas of 2 to 3 acres, Cover did not seem to be as important 
to these birds as to broods. 
19, Diving ducks preferred small cattail and hardstem-bulrush potholes for 
nesting. The heaviest per acre use occurred in semipermanent cattail areas. The 
locations of neither diving-duck nor river-duck nests appeared to depend on the 
presence of territorial or brood-rearing areas in the immediate vicinity. 
20. On attainment of flight, the young preferred large open potholes, River 
ducks made considerable use of flooded fields while canvasback used only the 
deepest pothole on the study area. 
21. It was concluded that management of waterfowl breeding habitat in regions 
of small water areas is dependent upon the maintenance of a proper interspersion of 
pothole types, each to serve its own function. We should therefore be concerned 
with management of the pothole habitat as a whole rather than with the manipulation 
of the characteristics of individual areas, 
