Mortality as a rule occurred during the first two or three weeks after hatching. 
Causes of this mortality were, however, difficult to ascertain. 
Productivity of the Area 
A count of breeding pairs on the area was made during the second week 
of May. The number of pairs of breeding birds seen on all potholes was recorded 
during both the early morning and evening hours, In every case an attempt was 
made not to flush the birds from the water area. This count was continued for 
four successive days and then a definite number of pairs was assigned to each 
pothole. Lone drakes and lone females were counted as separate pairs. Although 
the census was made during a time when many of the mallard and pintail hens 
were incubating, there is little doubt that most were observed during the evening 
counts, for they generally fed in the potholes at that time. 
A brood survey of the area was carried out on July 11. Each quarter 
section was assigned to two people and a simultaneous count of the entire area was 
made. The two observers walked through the emergent vegetation and surrounding 
grassland of all potholes on the quarter. Flushed and feigning hens were recorded 
as broods. 
Similar data were also collected in 1950 and 1951. Data collected during 
the three years, are compared to the 1949 production counts of Evans (loc. cit. ) 
in the following table. 
Table I} - Productivity of the Area - 1949 through 1952 

Pairs per square mile Broods per square mile 
Species 1949 1950 1951* 1952 1949 1950* 1951 1952 
Mallard 30.4 22.0 36 9.3 10.7 12.0 
Blue -winged teal 17.7 27.3 20.7 6.6 % 3, dled 
Canvasback 10.8 10.7 8.0 7.3 se 5,3 
Pintail 5.4 3.3 123 4.0 2.0 z.0 
Baldpate 5.4 2.7 8.0 553 3.3 4.0 
Shoveler 3.8 8.0 2.7 1.3 ae | 2% 
Green-winged teal Le 5 - a3 1.3 2.0 L.3 
Ruddy 5.4 4.0 oy 7% 5.3 4.0 2.7 
Redhead 5.4 4.7 2.7 4.7 4.7 zt 
Gadwall Dut 2.0 z.0 = 1.3 .7 
Scaup - 1.3 ol - 7 - 
Unidentified teal - - - 3.3 - - 
Unidentified } - - “ at - - 
Total 88.1 86.0 94.1 49.8 44.0 42.7 
Coot - 24.7 12.7 - 31.3 10.0 

* Data not comparable. 
