Table 9. The influence of area of open water on use by all broods 
Area of All permanment potholes Type Al _ potholes 
open water Number Brood-days Number Brood-days_ 

(acres) of Per Per acre of Per Per acre 
_..___ potholes pothole potholes pothole 
0.5 = 0.99 11 27.25 3.1 5 3.8 58.0 
1.0 = 19 6 58.5 9.7 5 38.6 33.3 
1.5 = 1.99 6 64.0 . 38.8 h 68.5 1.5 
2.0 - 2.9 2 140.0 65.1 2 140.0 65.1 
2.5 - 2.99 3 91.8 49.2 2 123.3 43.9 
3.0 - 3.19 1 100.0 31.3 1 100.0 31.3 
305 - 3.99 0 -<- --—- 0 --= = 
4.0 and over 1. 395.0 42.0 4) --+ ~-- 

°° 2 ee ee 
There was considerable variation in the preference for pothole size shown by 
the various species of ducks. Table 10, showing the species use of the 25 Type Al 
areas, indicates that the mallard prefers small areas while the canvasback and red- 
head use larger potholes. The blue-winged teal, baldpate, and pintail are more 
variable in size preference. Similar data relating to area of open water show a 
similar picture. However, the mallard and strangely emough the canvasback were the 
only species known to use potholes with 0.0 to 0.19 acre of open water. 
Cover Type ~~ Although there were too few potholes for comparisons to be made 
between different cover types in one size class, data based on all the potholes give 
the information shown in Table 1] relating to the use made of each of the cover 
types. Type Al received the greatest use, 1,332 brood-days, or 59.5 percent of the 
total; Type A3 was next in use, 587 brood-days, or 30.8 percent of the total. There 
was no use by broods of B2, B3, Bh, or D potholes. The heavy use of Al areas is 
probably due in part to the greater total acreage of this type. 
As shown in the second column, Type A3 received heaviest use per pothole, 
probably owing to the largé average size of these areas, The last column attempts 
to compensate for the variations in size by showing the use per acre of each type. 
(Acreage is figured on the basis of the entire pothole including marginal vegeta- 
tion.) Al (30. brood-days per acre) is the preferred type, closely followed by 
A3 (29.4 brood-days per acre), with A2 and Al. receiving a relatively small amount 
of use and the semipermanent and temporaries almost none. 
Table 11. Brood use of the 10 cover types. 
Pothole.  ‘lotal brood- Brood-days + + + bBrood-days 
type days in type per pothole per acre 
Al T, 33200 Se ; 30 Ly 
A2 165.0 27.5 19.4 
A3 687.0 171.8 29 
Al 31.5 | 4.5 3.6 
Bl 19.0 0.5 lei 
Be None None None 
B3 None None None 
Bu None None None 
C 1.5 0.1 0.2 
D None None None 
(rpg em eg PtP ct SSP a a 
Table 12 shows the preferences of the various species present in terms of 
percent acreage use (the percent of all use which occurred in the type divided by 
the percent of the pothole acreage made up of the type). 
