The location of nesting cover and of the nests themselves had only a 
slight influence on the distribution of breeding adults. Diving-duck pairs 
appeared to locate themselves in the neighborhood of nesting cover, but not 
necessarily in the same pothole. An exception to this was the ruddy duck, 
which apparently paired, nested, and raised its young mainly in one pothole. 
In only one case was nesting cover found to influence the distribution of 
breeding river ducks. This took place during the first two years of the study 
in the southwest corner of the study area, where 20 mallard nests were found 
in one hardstem-bulrush pothole and populations of this species were of more 
than average density in the immediate vicinity. In 1952, when the bulrush of 
this pothole was flooded out and useless as nesting cover, the use of the 
surrounding square mile by mallards was below the average for the study area. 
In 1953, use of the surrounding area by mallards was up, but late spring rains 
flooded out most over-water nesting and only one mallard nest was found in the 
pothole. 
Innumerable nest-hunting attempts by many obsérvers have led to the con- 
clusion that the nest of a pair of ducks is not generally located in or ad- 
jacent to the pothole on which the pair has been seen. At Waubay, the nest 
of one marked blue-winged teal hen was found more than a mile from the pothole 
on which the pair was seen most frequently, although it was within 50 yards of 
another pothole they were known to frequent. Two observations made at Min- 
nedosa, Manitoba, by Evans et al. (1952) also support this conclusion. There, 
two blue-winged teal nests were found immediately adjacent to a pothole which 
Was under observation at least twice daily, yet this pothole was never known 
to be occupied by this species. On one occasion, one of the hens was seen to 
leave her nest voluntarily and fly to a distance of at least half a mile, 
presumably to join her drake or to feed. Engeling (1950) found that the nest 
of the mottled duck in Texas may occur anywhere within the range of the pair, 
or even outside it. 
Although most species show at least a slight tendency to nest near water, 
it is not generally near the water on which they spend the most of their time. 
General observations of the behavior of birds and the distribution of nests 
gave the impression that they spent as little time as possible in the imme- 
diate nesting area. 
Broods 
The distribution of broods differed considerably from that of breeding 
adults. There was no longer a tendency to disperse, and there was a greater 
selectivity for definite types of water areas. 
Broods generally preferred the larger water areas, although data for 1951, 
1952, and 1953, when water levels were high, indicate that there is an upper 
size limit to preference, since areas of 2 to 5 acres were used more heavily 
than larger ones. During the brood season, most of the very small potholes 
(under 1 acre) were dry. Those that did retain water, or became refilled, 
were still not used by broods to any measurable extent. 
Most broods were found in open-water areas and deep marshes, as shown in 
table 12. In the high-water years of 1952 and 1953, there was an increase in 
ho 
