—Tina Yerkes, Ph.D.
While the fall migration of ducks and geese is eagerly anticipated and closely observed by waterfowl hunters, the spring migration usually receives much less attention. This is unfortunate as the return flight of waterfowl to their breeding grounds is one of the most amazing spectacles in the natural world. Huge concentrations of ducks and geese gather in places like Nebraska's Rainwater Basin, the Klamath Valley on the California-Oregon border, and the upper pools of the Mississippi River as the birds push northward along the retreating edge of the freeze line.
The spring migration is also one of the most important yet least understood periods in the annual cycle of waterfowl. Our current knowledge of migrating and wintering waterfowl ecology suggests that food availability is the primary factor limiting waterfowl populations outside of breeding season. During spring, birds must acquire large amounts of nutrients to fuel their extensive travels and meet their energetic needs when they arrive on the breeding grounds.
Unfortunately, some of the most significant wetland losses in the nation—in excess of 80 percent—have occurred in the Great Lakes and Upper Mississippi River watersheds, where waterfowl from both the Atlantic and Mississippi flyways migrate in spring. Given the large historic loss of wetland habitat in these regions, migrating waterfowl may not be able to acquire adequate food to meet their needs. And ongoing loss and degradation of remaining wetland habitat in these areas will only further limit the food resources available to migrating waterfowl. For example, recent research has documented that female scaup migrating through the Upper Mississippi River watershed have less body fat than they did 20 years ago. Since scaup and many other waterfowl don't appear to be leaving the wintering grounds in poor condition, loss or degradation of spring migration habitat and a resulting lack of food resources in these areas may be contributing to declines in scaup and other waterfowl populations.