2008 FEDERAL DUCK STAMP CONTEST Phone: 320-589-1001 |
The prairie pothole region covers some 300,000 square miles in central North America, including west-central Minnesota, home of the Morris Wetland Management District. This region gets its name from its once extensive grassland landscape that was dotted with millions of depressional wetlands called potholes. Before settlement, the prairie pothole region averaged an incredible 72 pothole wetlands per square mile. The combination of abundant shallow wetlands surrounded by vast grasslands served as ideal habitat for waterfowl and other prairie wildlife.
The rich prairie soils and favorable climate also provided conditions for successful agricultural production. Since the mid-1800's, 99% of Minnesota's once abundant prairies have been plowed and converted to farm fields, roads, or urban areas. Of the once numerous pothole wetlands, roughly 90% have been artificially drained or filled to make them suitable for agriculture or other uses. The pattern of wetland drainage is not uniform; some parts of the Morris district have few wetlands remaining and other areas still have a considerable base of wetlands providing habitat for wildlife. These remaining wetlands also provide important benefits for water quality and flood control as well as enriching people's quality of life through outdoor recreation.
The prairie pothole region remains the most important area in North America for waterfowl breeding. It is known as the continent's duck factory, responsible for more than 50% of the waterfowl raised each year in North America. Though the prairie pothole region has experienced massive habitat alterations, the area remains incredibly valuable for waterfowl, many shorebirds, grassland birds, and other wildlife.
Basic Waterfowl Breeding Ecology: Water + Grass = Ducks
Ducks depend on a cluster of wetlands of varying depth combined with abundant grasslands for successful breeding. It is the density of wetlands that dictates the density of the duck breeding population. In other words, more acres of wetland leads to more breeding pairs of ducks in any given area. Small shallow wetlands that hold water for only a few weeks or months are particularly valuable. Ten 1 acre wetlands will support more ducks than will one 10 acre wetland. It takes a dense cluster of wetlands to support good duck numbers. Waterfowl biologists call these clusters of wetlands a wetland complex. Deeper marshes, those which hold water throughout the summer, are where the hen raises her ducklings but, by themselves, these deep marshes can't support high duck populations. Deep lakes do not support large numbers of breeding ducks in the prairie region.
Once a certain number of ducks settle in an area to breed, it is the percentage of grassland that dictates what percentage of the nests hatch. Most duck nests are destroyed by predators before the eggs hatch. Human changes to the landscape and the loss of large predators have created an artificially high population of mid-sized predators like raccoon, skunk, and red fox; these species are all good at finding hidden nests and eating the eggs (foxes also often eat the hen). The best solution is to have at least 20% of the landscape for a mile in every direction in grass cover. In areas with 20% or higher grass cover, duck nests tend to be more successful, probably because the abundant grass cover provides predators other food sources (such as mice), makes the nests harder to find because the predator has to search more acres to find each nest, and because large grassland areas can support coyotes which displace red fox. Coyotes are not as tough on bird nests as are fox.
Geese have different breeding strategies and different preferred breeding habitat. In general, geese breed either north of the agricultural line (snow geese and many Canada geese, for example) or else prefer deeper, more permanent wetlands such as those still found in much of Minnesota. They also depend less on hiding their nest and more on defending their nest by chasing away mid-sized predators. Geese also do much more grazing of grass than do ducks. So, while ducks depend on shallow wetlands and grasslands, both of which tend to be destroyed in agricultural regions, geese either nest far north of the agricultural zone or, in the case of locally breeding Canada geese, thrive in the habitat we provide in abundance: lakes, deep marshes, grain fields, and mowed lawns.
