As described earlier, the movements of one shoveller brood on pothole No. 31 
were undoubtedly influenced by the activity about the camp. This did not prevent 
the brood from returning once the activity had ceased. 
A canvasback brood which spent 2 days in this same area showed considerable 
alarm at times of human activity and finally departed during the time that two 
visitors went swimming in the pothole. 
In August a wire drive trap was used on pothole No. 36 in an attempt to catch 
a brood of baldpates. This was done by placing the "V" type trap across the shore 
line with one wing extending out into the water and one up on shore. Repeated | 
attempts were made to drive the birds around the pothole through the marginal veg- 
etation and into the trap. This entailed a maximum amount of disturbance in the. 
form of beating the vegetation and shouting which lasted about 30 minutes on each 
trial, The first drive was made August 9, when the baldpates and a ruddy-duck 
- brood were present. On August 16, while the baldpate, a ruddy, and a redhead brood 
were present, two drives were made and the trap was left in position. On the evene 
ing of August 17 another drive was made and the trap was removed. The same three 
broods were later observed at the pothole indicating that it may be difficult to 
drive broods of at least these species from an area that is otherwise suitable, 
Age of 5roods -~ Table 15 shows the mobility of Class I and early Class ITI 
separated from the later Class II and Class III broods. Only those species are 
included for which there are at least six observations in each age group. Seven 
motherless broods which appeared to become immobile after the departure of the hen 
are excluded from the calculations. 
The mallard was the only species for which mobility decreased with age, while 
the average increase in mobility with age was 23.7 percent. It should be mentioned 
here that the data showinr the relation of movement to water levels shown in Plate 
XV were apparently not affected by the ages of the broods involved since both age 
groups were approximately equally represented, 
Table 15, Effect of age on brood mortality. 
Ss oe) cake Mle ge ae! ed Re of, mln ensnt Nope lal « 2) MODEL Uva , 
Species All ages Class I and early Late Class II 
on Class II and Class III 
Canvasback 1.5 13.9 16.9 
Mallard 13.6 15.2 13,0 
Blue-winged teal 8.6 7.5 10.8 
Pintail 19.6 15.8 2h.0 
Average W.1 13.1 16.2 

Mobility of Motherless Broods -- The desertion of broods by the females appar- 
ently had some bearing on their mobility since no motherless broods were known to 
move overland, Apparently most overland travel took place when the hens were present 
and perhaps was initiated by them. 
No deserted broods were found in shallow areas which showed signs of drying up. 
This may have been due either to efforts on the part of the hens to leave their young 
in suitable habitat or to chance, since the unstable areas received little use by any 
broods at the time most hens were leaving the area, 
