




STUDY AREA 
MANITOBA 
RAPID CITY 
NEST SURVEY AREA 
MINNEDOSA STUDY AREA 
—— ROADSIDE TRANSECTS 
Fig. 1. Minnedosa study area and nest survey area. 
larly important during drought periods, when most prairie 
potholes in southern Manitoba are dry. Erickson (1948) 
studied the life history and ecology of canvasbacks at 
Malheur National Wildlife Refuge in southeastern Oregon. 
Both Hochbaum and Erickson treated the general subject 
of habitat preference and use by canvasbacks. 
Stewart et al. (1958) reported that canvasback breeding 
populations were widely dispersed over prairies of southern 
Canada and the northern United States, as indicated by 
extensive annual aerial waterfowl inventories conducted by 
FWS. Several intensive waterfowl studies in Alberta, 
Saskatchewan, and Manitoba also indicated that canvas- 
backs were common breeders in the Canadian parklands 
(Smith 1971; Stoudt 1971; Kiel et al. 1972). Olson (1964) 
conducted a study in southwestern Manitoba comparing 
canvasback productivity on small prairie potholes, a large 
marsh, and a large shallow lake during the drought years 
of 1959-61. Although the occurrence of breeding canvas- 
backs was well documented throughout the pothole region 
of Canada, little information has been published regarding 
habitat requirements. 
The present work describes habitat relations of breed- 
ing canvasbacks in the aspen parklands of southwestern 
Manitoba near Minnedosa, during the 12-year period 
1961-72. Principal objectives were to delineate major 
habitat types used by canvasbacks during the breeding 
period and to investigate annual production, cover types, 
water fluctuations, predation, weather, and other factors. 
The Minnedosa study area was selected because previous 
investigations (Evans 1949; Dzubin 1955; Olson 1964; Kiel 
et al. 1972) had indicated a high density of breeding can- 
vasbacks in this region and had provided considerable back- 
ground information. 
Scientific names of animals and plants discussed in the 
text are listed in Appendix A. 
Study Area 
The Minnedosa study area is characterized by a diverse 
wetland complex ideal for breeding ducks (Kiel et al. 1972; 

Fig. 2. Wetland density in the Minnedosa study area (1967). 
Trauger and Stoudt 1974). Comparatively large, perma- 
nent wetlands are surrounded by excellent complexes of 
smaller wetlands that vary in permanency, size, shape, 
depth, vegetation, and land use. Quality of this waterfowl 
breeding habitat is influenced by a number of natural and 
human factors. 
The Minnedosa study area consisted of an extensive and 
an intensive unit within the Minnedosa District in south- 
western Manitoba (Fig. 1), The intensive unit, south of Min- 
nedosa, was used for counts of breeding pairs and broods, 
nest studies, and habitat appraisals. This unit consisted of 
a grid of roadside transects within a 181.3-km? area. These 
transects were 0.4 km wide (0.2 km on each side of the road) 
and covered a distance of 128.7 km (51.8 km?). The in- 
tensive unit contained from 15 to 33.6 wetlands/km? in May 
between 1961 and 1972, depending on annual water condi- 
tions (Fig. 2). During the 12-year period the average num- 
ber of ponds was 26.3/km?. Sections (259.2 ha) in the center 
of the intensive study area contained more ponds than did 
those along western and eastern edges of the area. The 
extensive unit, which included wetland habitats between 
Minnedosa and Shoal Lake, Manitoba (Fig. 1), was used 
as a source of additional information on nests. Evans et al. 
(1952) and Kiel et al. (1972) described waterfowl breed- 
ing habitat of the Minnedosa District in detail. 
Physiography 
The Newdale till plain is the principal glacial landform 
in the Minnedosa area. It is characterized by an extensive 
