Nesting Habitat
As the percentage of grassland in a landscape increases, so does the success of duck nests (Reynolds et al. 2000).
The Prairie Pothole Region of the United States and Canada is North America’s single most important waterfowl breeding area. Dotted with millions of shallow wetlands formed by glaciers 10,000 years ago, the Prairie Pothole Region encompasses over 250,000 square miles and supports more than 50 percent of the continent’s ducks in most years. In some portions of the region, potholes and their associated prairie uplands support over 100 breeding pairs of ducks per square mile.
Grasslands in the Praire Pothole Region
The Prairie Pothole Region is especially important to breeding northern pintails, mallards, canvasbacks, redheads, gadwall, blue-winged teal and northern shovelers. Currently, most ducks across the region have met or surpassed population goals established by the North American Waterfowl Management Plan (NAWMP) . One exception has been the northern pintail. This grassland-dependant duck has struggled despite generally favorable water conditions over the last decade. In fact, breeding pintail populations have decreased in excess of 50 percent in the last 20 years, with little sign of improvement. Factors limiting the comeback of pintail populations over the past few years are not entirely clear, although researchers suspect that poor nest success is the leading cause of the observed decline. Pintails typically settle on the breeding grounds in areas containing shallow wetlands that usually hold water only through early summer. Unfortunately, these are also the easiest wetlands to drain and many have been lost with the expansion of cropping practices. The areas that remain are subject to increased predation and disturbance due to highly fragmented nesting cover and to spring cropping practices.
Blue-winged teal, another species that has historically relied on the grasslands of North America for breeding habitat, have experienced population fluctuations that mirror the wet/dry cycle of the northern plains. Currently, the population is estimated at nearly 6 million, slightly down from 7.4 million in 2000. However, these numbers are above the NAWMP population goal of 4.5 million.
Several million ducks and geese use the Prairie Pothole Region each spring as breeding or 
stopover habitat during their spring and fall migration. Regions that have experienced substantial native prairie losses, such as Iowa, still offer valuable migration habitat in early spring when the ground is frozen and drain ditches are not yet flowing. Each autumn, an estimated 8 – 10 million ducks and almost one million geese migrate south through Iowa, en route to warmer climes. A few, including an estimated 106,000 ducks and 138,000 geese, remain during the winter in the Prairie Pothole Region or adjacent areas. However, the Prairie Pothole Region is most crucial for nesting waterfowl.
Other Grassland Benefits