pair were captured. What had been assumed to be the territory of one pair was 
apparently a zone of overlap between the home ranges of four pairs. 
Although we were unable to obtain significant data from marked birds of 
other species, it was evident from our repeated observations on a series of 
potholes in 1951 that the blue-winged teal had a relatively small home range 
compared with most other species. However, the general pattern appeared to 
be similar for at least the other puddle ducks. The potholes studied did not 
contain enough diving ducks to provide comparable information. 
Sowls (1951) found on a large marsh the same situation with respect to 
home range and territory as has been found on the Waubay study area. He 
noted that the area occupied by a pair of ducks during the nesting season may 
be better thought of as a home range, any part of which may be defended, de- 
pending upon the immediate reaction of the birds at the time. It appears that 
what the drake may be defending is his own proximity rather than a definite 
area; what causes him to be intolerant of other birds of the same species at 
one time and to be sociable an hour or so later is not known. 
The pair during the nesting season is therefore considerably more mobile 
than is often suspected. The area occupied by the pair is of considerable 
extent and the birds are able to react to changes in the habitat merely by 
moving to another more suitable pothole. Furthermore, this home range is not 
an area from which other pairs of the same species are excluded, and the home 
ranges of several pairs of the same species may overlap. The conflict between 
pairs when they come into proximity leads them to space themselves out and is 
very probably the factor which determines the carrying capacity of the habitat. 
Broods 
Once the eggs have hatched, the home range breaks down and the hen and 
brood, with a set of requirements and preferences different from those of the 
preeding pair, go off on a trek of their own. Figure 21 shows where 18 broods, 
individually marked on the nest in 1950, 1951, and 1953, were found after 
hatching. In no case was the actual route of travel or the ultimate destina- 
tion of these broods known. Even the four broods found on the pothole nearest 
their nests may have done some traveling between observations or after the 
last observation. The longest trip of 2-1/4 miles, made by a blue-winged teal 
brood, was accomplished before the brood was 2 weeks old. 
Movement overland did not seem to represent anything related to "home 
range." It appeared to be completely random, and there was no tendency to 
return toward the vicinity of the nest. No cause, such as drought or distur- 
bance, could be found to account for such movement. Although in some cases 
the pothole near which the brood hatched had dried up or become obviously 
unsuited to brood use, broods which left such potholes and were subsequently 
seen again must have, in the meantime, passed through suitable potholes which 
may or may not have been occupied by other broods of the same species. As 
-had been pointed out for the Manitoba parkland (Evans et al. 1952) such move- 
ment appears to be initiated by the hen, since no broods without hens were 
known to move overland. Furthermore, the hen can be assumed to be oriented 
to the landscape while she remains with the brood, as such hens were frequently 
45 
