27 
V. POTHOLE PREFERENCE AND FACTORS INFLUENCING MOVEMENT 
Some attention was paid to the characteristics of potholes and to the amant of 
use they received by broods, and it was possible to determine to some extent the 
relative attractiveness of various pothole types. 
On the basis of data on the mobility of species, the assumption is made that 
within limits broods can and do select those areas which are attractive to them. 
This ability to select varies with the mobility of the species, but in most cases 
this may be assumed to be great enough to provide an indication of preferences. 
It is difficult to determine what unit of measure is the most valid in deter- 
mining amount of use. Persons interested in managing areas where the uplands are 
of little value might wish to consider the number of broods per pothole. On the 
other hand, one wishing to evaluate the productivity on the basis of land or water 
area will be interested in broods per acre. So far as the author can determine, 
each method has its usefulness and where practicable figures will be expressed in 
broods per pothole and broods per acre, 
Size -- Table 8 shows the brood use of all the permanent potholes as influenced 
by size. The number of broods per pothole rises rapidly until a size of 2.5 to 3.0 
acres is reached where it falls off and again rises rapidly as size exceeds 3.5 
acres. The largest pothole on the area (10.9 acres) received the heaviest use in 
terms of broods per pothole but when use is expressed in terms of broods per acre, 
those areas of 2.5 to 3.0 acres were preferred, 
In order to exclude the influence of cover type, the same data are shown for 
the 25 Type Al potholes. Here the picture is similar although the greatest amount 
of use per pothole as well as per acre occurred in the 2.5 to 3.0 acres size class. 
It may be that if there had been large areas of this type, they would have been 
used more heavily. 
Table 8. The influence of pothole size on use by all broods. 
All permanent potholes Type Al potholes 
Pothole size Number ____ Brood-days Number Brood-days 
(acres) of Per Per acre of Per Per acre 
otholes othole potholes pothole 
0.0 - 0.49 3 0 0 2 0 0 
0.5 - 0.99 9 16.1 21.9 5 19.8 27.5 
1.0 = 1.h9 7 23.6 18.8 hy 33.7 26.5 
1.5 = 1.99 8 25.1 Wb. 6 32.9 18.6 
2.0 = 2.19 by 71.5 32.5 2 88.0 10.0 
2.5 -. 2.99 3 95.5 36.3 2 143.3 56.2 
3.0 - 3.9 2 61.0 20.0 1 93.0 31.0 
3.5 - 3.99 3 115.5 30.4 3 115.5 30.4 
4.0 and over 3 219.0 32.4 0 mates --- 

Table 9 illustrates the influence of area of open water. Again, there is a 
peak (in this case in the size class of 2.0 to 2.5 acres) which corresponds to 
potholes with total areas of 2.5 to 3.0 acres, but the 0.0 to 0.5 acre potholes 
(corresponding roughly to potholes with total areas of 0.0 to 0.99 acre) received 
almost as much use per acre as the larger waters. This is more nearly in agreement 
with the finding of Furniss (1935, 1938) who reports that in northern Saskatchewan 
the greatest use per acre was of potholes 0.0 to 0.5 acre in size. 
It was impossible to draw similar graphs for any of the other pothole types, 
since they did not occur in sufficient nunbers. 
