Effects of Predator Management and Parasitism on Over-Water Nesting Diving Duck Production in Southwestern Manitoba
Thesis - Open Access
Master of Science (MS)
Department / School
Natural Resource Management
Canvasback, over-water nesting ducks, predator management, redhead
Nest survival of upland nesting waterfowl (e.g., mallard [Anas platyrhynchos], blue-winged teal [Anas discors]) has been studied extensively in the Prairie Pothole Region (PPR) of North America. Conversely, over-water nesting diving ducks’ nest survival is poorly understood, likely because over-water nests are more challenging to find, may be less concentrated, and searching for these nests is physically demanding. Nest depredation is considered a leading cause of duck nest failure and is considered a limiting factor on upland nesting waterfowl production in the PPR. Similar factors limiting upland nesting duck production may limit over-water nesting duck productivity, but studies of this nature are lacking. Another limiting factor may be nest parasitism, an under looked attribute for some of these over-water nesting ducks (e.g., canvasbacks [Aythya valisineria]). Some species, particularly the redhead (Aythya americana), have adapted to habitat constraints by parasitizing other ducks’ nests. In previous studies, 30%–50% of canvasback nests were parasitized by redheads, with an average of 3 parasitic eggs laid per nest. For these studies we first evaluated the efficacy of predator trapping and removal on the survival of over-water duck nests of five focal species of diving ducks in Southwestern Manitoba. To further understand nest parasitism in diving ducks, we tracked host and parasitic eggs of redheads in canvasback nests in southwestern Manitoba, Canada, during the 2019 and 2020 nesting seasons. We counted all eggs found at host nest sites and classified eggs as successful, lost to parasitism, or depredated. Although mean nest survival was greater on traditional trapped sites, confidence interval estimates indicated an equivocal treatment effect. Thus, trapping predators had, at best, a modest positive influence on survival of over-water duck nests and did not generally appear to be an effective way to increase nest survival for these five focal species. We do, however, suggest that redhead parasitism may be a factor limiting canvasback productivity in our study area and deserves further investigation.
Library of Congress Subject Headings
Aythya -- Nests -- Manitoba.
Aythya -- Predators of -- Manitoba.
Aythya -- Parasites -- Manitoba.
Ducks -- Nests -- Manitoba.
Ducks -- Predators of -- Manitoba.
Ducks -- Parasites -- Manitoba.
Number of Pages
South Dakota State University
Rohrer, Trenton E., "Effects of Predator Management and Parasitism on Over-Water Nesting Diving Duck Production in Southwestern Manitoba" (2021). Electronic Theses and Dissertations. 5829.
Ecology and Evolutionary Biology Commons, Natural Resources Management and Policy Commons, Ornithology Commons