The main goal of our research is to acquire information needed for waterfowl managers to determine the most efficient way to elevate and maintain duck populations at levels set forth by the North American Waterfowl Management Plan (NAWMP). Waterfowl populations’ breeding in the prairie pothole region of North America are most likely limited by there ability to reproduce. Of the factors that impact reproduction, nest success is proposed to have the greatest impact on duck abundance.
Past predator removal studies have demonstrated dramatic increases in nest success. Most of these studies have been conducted in the prairie pothole region of the US, an area that currently supports greater than 50% of the North American breeding duck population. Another important breeding area for North American ducks is the prairie parkland region of Canada. The prairie parkland region is a transitional zone between the prairie potholes and the boreal forest. This region often contains grasslands similar to those in the prairie potholes, integrated with the more permanent wetlands of the boreal forest. In addition to the more permanent wetlands, the parkland has more woody vegetation that is often used by predators, thus may support a greater density of nest predators than the prairie potholes region. In fact, 1 study found nest success of ground nesting ducks dropped below 1% in some years, a much lower success rate relative to the 10 - 20 % often observed in the prairie potholes. Because of differences in wetland variability and habitat structure (amount of trees and other woody vegetation) and a presumed greater abundance of nest predators, it is unclear if predator removal in the parklands will lead to an increase in nest success similar to the increase observed in previous Delta studies in the prairie pothole region. Another aspect of our research will determine how hens may assess predator density and determine how predator density influences reproductive investment of the nesting hen. Scientific theory suggests, when hens are more likely to reproduce successfully, for example, when nest predators are reduced, hens should invest more into reproduction. Understanding if hens can assess predator density and alter their reproductive investment accordingly is important from a management perspective because it could play a large role in how we manage habitat for waterfowl. For example, we may learn that hens may not maximize their reproductive investment even when good nesting habitat is available if nest predator densities are high, demonstrating an additional value in reducing predator densities. In order for a hen to increase reproductive investment when predator densities are low, however, the hen must be able to determine relative density of predators. In other words, the hens must have some way to assess predator densities when choosing their nest site. The final goal of the project is to test the hypothesis that ducks can assess predator densities by viewing ultraviolet light reflecting off predator urine and, therefore, can choose a nest sight with the lowest density of predators. Results from the 3 components of this project should help guide waterfowl managers when making decisions regarding how habitat should be managed to maximize reproductive success of ground nesting ducks throughout North America.
