Table 14.--Relative mobility of duck broods at Minnedosa, Manitoba, 1949 
[From Evans et al. 1952] 
Number of Average number of 
Species observations days per pothole ' 
Pintail 5 
Canvasback 7 
Mallard vi 
Redhead Ll 
Blue-winged teal 11 
Baldpate 20 
Ruddy 233 

ifhe study terminated before many broods of this species had reached flying 
age, so this figure is low. 
than the baldpate or ruddy duck. All but the ruddy duck, only one brood of 
which was found to move overland, generally made use of several potholes be- 
tween hatching and flying. 
There is no evidence that such movement brings about an increase in 
losses to predators, and since such movement is toward better habitat it is 
very likely that the opposite is true. 
These data concerning the mobility of pairs and broods clearly indicate 
that most species of ducks may often move a mile or two with little difficulty. 
Fair-weather loafing sites for the pair need not be on the same pothole as 
cover used in stormy weather, which can be at a considerable distance. It is 
desirable that nesting cover be somewhere nearby, but it need not be adjacent. 
Furthermore, it can be at a considerable distance from permanent brood water, 
since a brood can easily travel a mile or so to water as the potholes used 
by the pair dry up. 
USE OF THE HABITAT AND THE LIMITING FACTORS 
We have noted something of the relation of the changing requirements of 
the breeding population to a highly variable habitat. Jt has been pointed 
out that breeding birds in the spring were responsive to conditions that 
enabled them to disperse and remain separated from other pairs of the same 
species. They showed little preference for areas especially attractive from 
the standpoint of food, cover, or any other measurable factor. Clearly, at 
this time they sought space and freedom from interference, and it is probable 
that the ability to find such isolation had an effect on the productivity of 
the birds as individuals, as well as on the carrying capacity of a given area. 
We have seen that the ability to disperse, as determined by spring runoff and 
rains, was highly variable from year to year, even between four “near normal" 
years. 
48 
