Effects of Habitat and Predator Manipulations on Prairie Ducks:
Management by Experimentation
THOMAS D. NUDDS AND ROBERT G. CLARK
Department of Zoology, University of Guelph, ON MIG 2WI, Canada;
Canadian Wildlife Service, 115 Perimeter Road,
Saskatoon, SK S7N OX4, Canada
Properly conducted experiments can provide the best knowledge upon which to base management decisions. Frequently, in crisis situations, action must be taken in the absence of complete information about the available management techniques, but management is often implemented in ways that are not easily evaluated for effectiveness. Proposed habitat and predator manipulations to increase population sizes of some species of prairie-nesting ducks by increasing nest success depend critically on some as yet poorly understood relationships among rates of nest predation, type of nest predator, nest concealment, nest and predator densities, and habitat (patch) size. Each of two schools of thought about how best to achieve the goals of the North American Waterfowl Management Plan through the Prairie Habitat Joint Venture agrees that (1) high rates of nest predation limit recruitment and (2) that nest survival is the most important "bottleneck." However, one school offers that either direct removal of nest predators, or deterring them with some combination of dense nesting cover and electric fencing on small tracts of land, should be used to increase nest success. The other school offers that large-scale restoration of marginal farmlands would allow ducks to disperse nests at low densities and cause nest predators to have low foraging success. We outline an experimental protocol developed around an indicator-variable regression model to (1) evaluate various habitat management proposals to reduce nest predation and augment recruitment; (2) examine factors affecting nest, duckling, and overwinter survival among birds nesting in managed habitat; and (3) detemine the minimum patch size that needs to be acquired in order to sustain duck nest densities and nest success at historical levels. The exercise illustrates a way in which habitat management programs can be implemented to maximize knowledge gained.
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