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Importance of Individual Species of Predators on Nesting Success of Ducks in the Canadian Prairie Pothole Region

Study Areas

The Canadian Prairie Pothole Region includes about 480 000 km² of parkland and grassland. Deciduous woodland along the northern and eastern edges gradually gives way toward the southwest to grassland interspersed with small areas of woods, and then to open grassland. The topography is mostly flat or gently rolling. Glacially formed wetlands abound, with an average of about 21/km² (Gollop 1965). The Parkland Region has a subhumid climate; that of the Grassland Region is semiarid. Both regions have cold winters and warm summers; snow melts in most years during late March and April.

Fieldwork was conducted during 1983-1985 on 16 study areas distributed throughout the Canadian Prairie Pothole Region (Fig. 1). Study areas were located along air-ground segments of aerial survey transects used by the Canadian Wildlife Service and the United States Fish and Wildlife Service in estimating annual size of waterfowl breeding populations (Bellrose 1980, pp. 18-19). The study areas are considered to be representative of the principal duck nesting habitats of the Prairie Pothole Region in Canada. Each study area was studied for 1-3 years during 1983-1985, for a total of 30 study area - years.

Fig. 1.  Study areas in the parkland (shaded area) and grassland (unshaded area south of parkland) portions of the Canadian Prairie Pothole Region.

Each study area was 16 km long × 1.6 km wide and had a road (or in some places a trail) extending lengthwise through its center. Each study area was divided into 40 legal quarter sections (hereinafter termed quarters, each 0.65 km²), which we used as sampling units.

Nearly all upland on each study area was cultivated annually for production of small grain or was grazed by cattle. Occupied and abandoned farmsteads were scattered throughout each study area. Other habitats consisted primarily of wetland fringes, small areas that were not used for agriculture, and wooded areas. Some wooded areas were present throughout most study areas, but they were most numerous in the Parkland Region, where aspen (principally Populus tremuloides), often with an understory of hazelnut (Corylus americana), or willow (Salix sp.), was prevalent around wetlands and in woodlots. Most trees in the Grassland Region had been planted, primarily as single-row shelterbelts in fields or as windbreaks at farmsteads.

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