30 
Table 12. Percent acreage-use value for the 10 pothole types as 
determined by brood occupancy (calculated). 
Percent acreage-use = _ Percent use of type 
Percent acreage of pe 
Pothole type 
| 


Al A2. A3 Al Bl B2 B3 BB C D 
All broods ° 
Baldpate Cote Bley -- -- -_ -- -- -- -- -— 
Blue-winged teal ley 0.6 2.2 O12 -- -- -- -- -- -- 
Canvasback 1.7 0.7 1.5 -- 0.1 -- a ~~ — 
Gadwall 0.1 aay 39 Ze 3 wa =. bar tel = oe bdomad 
Green-winged teal 1.8 -- 1.6 -- -~ -- -- -- -- -- 
Mallard 1.8 1.1 0.9 O18 O.1 -- -- -- trace -- 
Pintail 223 -- 0.2 O.1 0.5 -- -- -- -- -— 
Redhead 2.2 -- 0,8 -- ~- -- -- -- -+ oe 
Ruddy O.6.mtO2eets,8 he Cee SS. lige anche eee me 
Shoveller 0.5 8.2 0.7 0.5 -- -- ~-- -- -- -~ 

The mallard was apparently the most adaptable species, as it was the only one 
found in temporary waters and it made more use of Al; potholes than did others. The 
baldpate and ruddy were apparently the least tolerant. The relatively heavy use of 
Type A2 by baldpates all occurred in pothole No. 39, which is on the borderline 
between Type Al and Type A2, indicating that this species was fairly dependent on 
the former. The ruddy, on the other hand, was apparently dependent on the hardstem- 
bulrush areas. This may have been due to its low mobility which made it unlikely 
that broods of the species would leave the potholes which were preferred as nesting 
cover, Blue-winged teal and canvasback broods appeared fairly tolerant to varying 
conditions, but still showed preference for Types Al and A3. Both redhead and 
pintail showed definite preference for Type Al, the former species appearing to 
be the more adaptable as it made some use of aL and Bl areas. The preference of 
the shoveller for Type A2 was quite clear-cut, since very little of the time spent 
in this type was in areas resembling Al potholes as occurred in the baldpate. Data 
on the green-winged teal and gadwall are included but are undoubtedly of very little 
Sipnificance owing to the small number of broods of these species using the area, 
Rainfall -- By means of the data in Plate Xlb it was possible to calculate 
the daily fluctuations in mobility of one species. Each day's mobility may be 
calculated as the number of terminations of residence divided by the number of 
broods involved. Since this furnished a very scattered graph, it was smoothed 
out by using a moving average of three consecutive daily readings of the data 
from Plate XIb. 
The daily fluctuations in mobility of the canvasback are shown in Plate XV. 
The only period for which these data are valid is that during which there were few 
broods newly hatched and few flying. Since broods were aged in only three classes 
it was impossible to determine the status of individual broods in this respect. 
However, Plate XIV shows that during the period from July 2 to August 1, the age 
composition of the population was relatively stable and there was a minimum of five 
broods each day so that data for this period should be significant. Two definite 
peaks in mobility occurred during this period. These peaks may be offset to some 
extent by error in calculating the exact day a brood moved into or deserted an 
area and they are somewhat spread by the moving average, but they indicate a 
definite increase of movement on or about these dates. 
The possible significance of these periods of high mobility may be seen when 
they are compared with the dates of the two heavy rains which occurred during July, 
