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Pair Density and Reproductive Performance of Ducks in a
Low-predator Environment

I. J. BALL AND ROBERT L. ENG

Montana Cooperative Wildlife Research Unit, University of Montana,
Missoula, MT 59812; Fish and Wildlife Management, Department of
Biology, Montana State University, Bozeman, MT 59717

We studied the density and productivity of breeding ducks inhabiting 177 stockdams (179 surface ha) on large expanses of grasslands in north-central Montana. Upland cover conditions were poor by conventional standards over most of the area, consisting mainly of sparse short grasses, cactus, and scattered sagebrush. However, predator populations also were low and consisted mainly of coyotes. The 1987 breeding population of ducks was estimated at 1,379 breeding pairs, 7.8 pairs per pond, and 7.7 pairs per ha of water. Mallards averaged 1.1 pairs per pond, and pintails 1.0 pairs per pond. Thus, although pond numbers were low in comparison to much of the Prairie Pothole Region, the density of breeding pairs per ha of water was higher on our study area in 1987 than in prime prairie pothole areas during the 1950s and 1960s. Productivity also was high on our study arm (GIF -- mean symbol=48 broods per 100 pairs of dabbling ducks). The high density and productivity of ducks associated with stockdams and unfragmented tracts of western grazing lands is easily overlooked because the dams themselves are widely scattered. Management activities should focus on preventing further conversion of grassland to cropland and on constructing water areas to support more pairs in an environment where nest success is high. Some of the management practices developed in the Prairie Pothole Region to improve nest success are unnecessary on western rangeland and may be counter-productive.
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