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Distribution and Abundance of Predators that Affect
Duck Production: Prairie Pothole Region

Predator Surveys


Predator surveys were conducted to determine the distribution and relative abundance of each predator species in each study area. Surveys had to be simple and easily integrated with other study objectives, namely obtaining data on nest success in ducks. For most predator species, proven methodology for assessing abundance was unavailable or cost prohibitive (Clark and Andrews 1982; Greenwood et al. 1985). Therefore, we devised a variety of survey methods that could be systematically applied during the duck nesting season, allowing us to capitalize on observations by the numerous individuals already working in each study area. Spring is a good time to survey predator populations because most predators are caring for young. As a result, surveys can be conducted when populations are relatively stable (little emigration or immigration) and comprised of relatively evenly spaced social groups. More than one survey method was used for some species (Appendix Table 1). (Results from all surveys by study area and year are provided in the Appendix to enable others to combine or use data differently.)

Predators were surveyed by persons or crews whose primary duty was to gather data on nest success in ducks, by other biologists working in the study areas, and by specialists in surveys of predators who moved among study areas. Each crew was responsible for gathering data in two or three study areas in a given year. Individuals responsible for conducting surveys and for maintaining records were instructed in survey methods and given written survey guidelines.

The surveys of predators consisted of (1) livetrapping striped skunks, (2) livetrapping Franklin's ground squirrels, (3) counting carnivore tracks, (4) recording sightings of predators, (5) counting American crows and black-billed magpies along road transects, and (6) recording locations of occupied nests of avian predators. However, not all surveys were conducted each year or in all study areas (Appendix Table 1). In addition to conducting the described surveys, field personnel were asked to record locations of active coyote and red fox rearing dens (dens with pups) and to record information about predator species not accommodated in the systematic surveys. Sources of supplementary data were aerial searches for coyote and red fox rearing dens (Sergeant et al.1975) in about half of each small unit management study area and records of predators removed from federal lands in central portions of three small unit management study areas.

All surveys except counts of American crows and black-billed magpies along road transects in two study areas (Morgan, Plentywood) and records of predator sightings were conducted inside study areas. The road-transect counts of American crows and black-billed magpies for two study areas (Morgan, Plentywood) were conducted primarily along roads adjacent to each area because of absence of a center road. Data on predator sightings in the small unit management study areas and in some other study areas included time spent in lands adjacent (<2.4 km) to those areas, where some study personnel were also required to work. All data from surveys of predators except sightings were recorded by quarter section or combinations of quarter sections.

The removal of predators from three study areas (Eldridge, Fredonia, Lake Park) was part of the small unit management study. The removal was conducted annually from early April through late June in a 63-303 ha tract of federal land in the center of each area (Appendix Table 3).


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