Let's Count Ducks
waterfowl in North America are remarkably well surveyed. The traditional survey area, or TSA, includes the prairies, Canada's western boreal forest, and Alaska
. Breeding surveys are also conducted in eastern Canada, the northeastern United States, and parts of the Midwest, as well as in California
, and Nevada
. In 2012, these surveys counted 54 million breeding ducks (total ducks, not pairs), with 48.6 million in the TSA. Sixty percent of these birds were found on the Canadian and U.S. prairies
. Another 30 percent of breeding ducks were counted in Alaska and Canada's western boreal forest. This broad region plays an important role in maintaining continental waterfowl populations by supporting relatively stable numbers of breeding birds, which make a fairly consistent contribution to the fall flight each year. Surveys outside the TSA claimed the rest.
To estimate how large presettlement duck populations might have been, we need to mentally rebuild the duck factory. Prairie breeding ducks use three types of wetlands. Temporary wetlands are the most common and typically hold water for only one to three weeks in spring. In dry years most temporary wetlands hold no water at all. Seasonal wetlands are the second most abundant breeding habitat and are wet anywhere from three weeks to three months each year. Semipermanent wetlands are the least common, though they may hold water for several years at a time.
There is a strong relationship between duck numbers and the abundance of temporary and seasonal wetlands. Every temporary or seasonal wetland lost on the prairies can mean one less pair of breeding ducks.
Prior to settlement, 95 percent of all prairie wetlands were temporary or seasonal. Knowing how many of these wetlands were lost provides a clue to the number of ducks the prairies once supported.
don't automatically come to mind when we think of the Prairie Pothole Region
. However, both states were once a vital part of North America's duck factory. In fact, Iowa may have once hosted 2 million pairs of breeding ducks, about the same as today's densities in North Dakota
. Unfortunately, the state has lost 95 percent of its temporary and seasonal wetlands, and now supports just 150,000 breeding pairs. The situation in Minnesota isn't much better. Eighty percent of this state's original temporary and seasonal wetlands are gone. Prior to settlement, western Minnesota may have supported 2 million pairs of breeding ducks compared to 375,000 today.