75 
Receding water levels influenced brood movement especially if the 
water line was below the edge of the emergent vegetation. Concentrations of 
broods were noted on some of the deeper potholes as early as the middle of June. 
Sufficient water areas to insure a successful brood season, remained on the area 
throughout the season. Very few flightless broods were seen after August 20. 
However, it seems probable that unless there are some abnormally heavy fall 
rains or a superabundant snowfall this winter, many of the potholes will not 
contain sufficient water to hold breeding pairs in the spring. 
