Defenders Magazine

Wings Over the Prairie

Celebrating a place of sky, pools and birds: the prairie potholes.

By Douglas H. Chadwick

© Cliff Beittel

So much sky. And below, a seemingly infinite number of pools to mirror it, catching each dawn color and passing cloud. Such a setting almost calls aloud for wings. They arrive in a springtime rush that begins with mallards and pintails, along with snow geese touching down to refuel on their way north. Next come migrating swans and cranes, accompanied by great, gabbling throngs of blue-winged teal, gadwalls, shovelers, wigeons, redheads and canvasbacks that stay on to breed. Then the shorebirds -- marbled godwits, Wilson's phalaropes, piping plovers, American avocets and a skittering host of others -- followed by songbirds, from sedge wrens picking mayflies off marsh plants to bobolinks seeking a drink. The longer the days grow, the more that huge dome of sky fills with the voices and grace of feathered bodies in flight.

This place of sky and pools, known as the prairie potholes region, lies at the very heart of North America. Although mention of the name may draw blank stares from many Americans, bird aficionados know the region well: It provides food and rest for more than 300 bird species, about 180 of which stay here to nest. In a good year, at least 20 million adult and newly fledged ducks lift off from these wetlands to begin winging south in the fall. That's half the total on the continent, arising from just 10 percent of its total breeding habitat.

The potholes are usually less than six feet deep and sit in some of the most fertile soils on Earth. During the region's long, hot summers, the shallow pools turn into broths of microbes, aquatic plants, insect larvae, and other animals -- a life soup for birds. While hiking in North Dakota, I looped between countless glimmering saucers of this soup picturing every bird's bill as a spoon. In addition to their nourishment, the very smallness of typical potholes helps multiply ducks. Because of the birds' territoriality, only one or two breeding pairs may share a five-acre pond, whereas five one-acre ponds will hold a pair each.

Ice Age glaciers gouged this terrain and withdrew 10,000 to 12,000 years ago, abandoning a jumble of freshly ground stone and silt mixed with chunks of buried ice. As the chunks melted, they left depressions to collect moisture from snow and rain. When European settlers arrived, there were 25 million of these potholes spread across 310,000 square miles of the continent, from eastern Alberta through southern Manitoba in Canada and from eastern Montana across the Dakotas into southern Minnesota and Iowa in the United States -- an average of 83 every square mile.

Pothole has another connotation in our society, however. It is an obstacle in the road of progress -- something that needs to be filled in. And since settlement began, more than half the original prairie potholes have indeed been filled, or drained, and plowed into oblivion. Another 20 percent or so are severely degraded. And while various regulations have lately been put in place to stem the outright destruction of potholes, farmers can still plow, burn, spray and harvest right up to their edges.

And the edges are almost as important as the potholes themselves. All kinds of waterbirds from sora rails to pied-billed grebes depend on the bulrushes, cattails and sedges that border the open water in rings, while ducks will nest as far as several miles beyond. Intensive agriculture destroys some nests directly and removes wild grains and insects that fuel growing broods. Grazing and farming also strip away cover that conceals nests from predators. Ironically, this problem is magnified by campaigns against coyotes, the largest carnivores left in the region. Although they do eat waterfowl and other birds, these "brush wolves" are an invaluable natural check on far more effective nest predators such as red foxes and raccoons. Coyote control efforts thus amount to unwitting bird reduction programs.

Fully functional prairie potholes are so spectacularly productive that they may even act as significant carbon sinks, helping to counter global warming. As they study this wetland complex more fully, scientists are coming to understand its richness as part of a much larger ecosystem in far greater peril. The Great Plains were the most extensive grasslands on Earth. Only a fraction of one percent of the tallgrass prairie remains today, and undisturbed native shortgrass prairie and mixed-grass prairie are both becoming rare. Once-common grassland bird species -- Baird's sparrow, dickcissel, lark bunting and a host of others -- bear witness to this trend. Over the past quarter-century, they have undergone a broader, steeper decline than any other North American bird group.

Given the region's reputation as a duck factory, sportsmen and wildlife managers were the first to defend its remaining lakes and ponds. More recent projects include the Prairie Potholes Joint Venture, in which private groups team up with state and federal agencies to purchase critical acreage and protective easements from willing sellers. A landscape-level approach to safeguarding habitats, it reflects a growing realization that saving wetlands in the continent's core means saving grasslands as well. A sky the size of the one out here desperately needs a conservation vision almost as big to keep it full of wings.

Montana resident Douglas H. Chadwick is an author and biologist with a longstanding interest in the often-overlooked habitats and species of America's heartland.