Table 13.--Average percentage of broods using each wetland t 1950-53 

[Based on 1,618 brood observations ] 



Number ‘ Percentage of broods using-- 
obser- Intermittent | Temporary |} Shallow] Deep water 
Species vations areas marshes } marshes | marshes | areas 
B-W Teal 60.0 
Gadwall 82.8 
Mallard 548 
Pintail 58.1 
Shoveller 63.1 
Canvasback 88.0 
Redhead Oh 
Lesser Scaup 100.0 
Ruddy 64.7 
Other 60.0 

2. Potholes less than 1 acre in size were not heavily used by broods. 
3. Species may be tentatively rated in order of decreasing demands for 
deep water as follows: canvasback, lesser scaup, redhead, gadwall, ruddy duck, 
baldpate, shoveller, green-winged teal, blue-winged teal, mallard, and pintail. 
They also rate in the same order with regard to increasing demand for, and use 
of, escape cover. 
4. Areas with no cover were used by broods if they were at least 20 inches 
deep and 5 acres in size. 
5. River-duck broods (except gadwall) made free use of areas as small as 
1 acre and as shallow as 5 inches provided that good escape cover was present. 
6. Potholes less than 20 inches deep and 2 acres in size, and totally 
overgrown, were seldom used by diving-duck or gadwall broods. 
7. A rise in water levels may lead to increased brood use of marsh types, 
as shown in table le. 
The same statements regarding the influence of food and water chemistry 
on the distribution of pairs may be applied also to broods. Although no 
detailed studies were made of food requirements or available food, it appeared 
to be abundant in all potholes. There were a few potholes which, in the late 
summer of 1950, appeared to be turning alkaline as water levels dropped and 
dissolved solids became more concentrated. However, they were by that time so 
shallow that it is doubtful whether broods would have used them in any event. 
ho 
