Johnson Research - Canada
Productivity of Over-Water Nesting Ducks in SW Manitoba.
Michael K. Johnson (MS Candidate)
Todd W. Arnold (Advisor/Professor, Dept of Fisheries, Wildlife, and Conservation Biology)
During the last 3 years (2015-2017), Delta Waterfowl Foundation and the University of Minnesota have been investigating the productivity of over-water nesting ducks (a.k.a. “diving ducks”) in the prairie-parkland region of Manitoba. This area is characterized by high-densities of permanent and semi-permanent wetlands which provide the stable water conditions that this guild of ducks depends on. This area has been popular for waterfowl biologists studying the breeding ecology of these birds for over 60 years, and it is thought to host the highest densities of over-water nests in all of Canada. Research has proved that these ducks are highly susceptible to drought conditions given their dependence on water for nest construction, and local land use practices have altered the landscape decreasing the amount of ideal nesting habitat available. The objectives of this project have been to measure productivity using more efficient methodology, and investigate responses in nest success under an alternative management technique proven to increase nest success with upland nesting ducks in the prairie-pothole region.
Justification for this project stems from challenges associated with studying these birds and their long-term population trends. Traditional productivity estimates require active nest monitoring and locating over-water nests is a laborious process requiring an army of individuals to spend many days among the inundated vegetation in wetlands. Refining survey techniques could eliminate the need to locate nests, allowing managers to allocate time and personnel towards increasing the size of the area covered. Long-term population trends for diving ducks have responded to precipitation trends and land use practices in various ways depending on species. Some species have increased almost exponentially, while others sharing the same habitat have remained stable, or even declined. This has been the case since the mid-1990s and managers have been searching for alternative management techniques to boost nest success, as this is one of the most important drivers of population growth. Predator reduction has been successfully implemented in the prairie-pothole region and efforts have expanded north of the border with the intentions of improving recruitment in over-water nesting ducks.
Data collection begins in late April- early May, when breeding pairs return to the nesting grounds, and concludes during the first week of August when broods of ducklings are beginning to develop their adult feathers for flight. Data recorded during the summer months has revealed a strong and consistent nesting effort across much of the study area, producing a robust sample of nests to draw inferences of survival from. Waterfowl surveys appeared to line-up with assumptions at first, but numerous years of data have resulted in less consistent results which may require additional time to make sense of. As this project wraps up, we have learned that repeated measures are very important when testing new survey and management methods, as multiple years can provide the range of conditions necessary to fully test assumptions and hypothesis under multiple scenarios.