Date of Award
Master of Science
Natural Resource Ecology and Management
Adam K Janke
Wetlands in the Prairie Pothole Region (PPR) provide important stopover areas for spring migrating ducks in transit to northern breeding areas. However, how ducks use and distribute among different wetland types found in the agriculturally-dominated landscapes of the southern PPR is unknown. The goals of this study were to (1) determine factors affecting the use of spring-migrating ducks on wetland types present in the PPR and to (2) calculate activity budgets of ducks on different wetland types within the Iowa Prairie Pothole Region. We conducted weekly duck surveys during the springs of 2018-19 and surveyed a total of 1,061 wetlands within the PPR of Iowa. We observed approximately 131,000 ducks for a total of more than 1 million duck use- days. The majority of ducks counted in the study concentrated on a few key wetlands, primarily large semi-permanent wetlands. Semi-permanent wetlands provided the most duck use days overall and by a per unit area compared with the other wetland types including farmed wetlands, seasonal wetlands, and lakes. In addition to wetland area, duck use- days were influenced by wetland depth (mean, maximum), and the structure and percent of emergent vegetation on semi-permanent wetlands. We found dabbling ducks had a quadratic relationship with the percent of emergent vegetation while diving ducks were negatively related to the percent of vegetation. The structure of emergent vegetation had variable relationships with the abundances of duck species, although we observed the highest abundances on wetlands with areas of interspersed emergent vegetation and open water. Seasonal and farmed wetlands had inconsistent duck use, apparently due to variable water presence and duration in these wetland types. The number of visits flooded (+) and crop type were important factors for farmed wetlands while wetland area (+), percent vegetation (-) and vegetation height (+) were important for seasonal wetlands. Despite relatively low use, we found these wetlands may still contribute important habitat for spring migrants, with high percentages of time spent feeding and resting compared to semi-permanent wetlands. These results suggest that large, semi-permanent wetlands, which provided the most duck use, were important for transitioning ducks through this region. However, the other wetland types may also provide important habitat, especially because of the abundance on the landscape.
Ballard, Derek, "Wetland use by spring migrating ducks in Iowa’s Prairie Pothole Region" (2020). Graduate Theses and Dissertations. 18091.