As the annual spring waterfowl migration begins this month, lesser scaup, often called bluebills, will once again be migrating through Iowa on their way to more northern breeding areas. Lesser scaup were once extremely abundant on Iowa wetlands during the spring and fall migrations. Sadly, however, they are not as abundant as they once were. Population surveys indicate that scaup populations have declined steadily over the past 25 years. In an attempt to uncover the underlying reasons for this decline, waterfowl researchers from Louisiana State University, US Geological Survey, USFWS, DU, and several Midwest state conservation agencies, including the Iowa DNR, have joined forces to examine the body condition of female scaup as they migrate across the Midwest this spring. In addition, researchers will be looking at the wetlands that these scaup use during their northward migration to determine if they contain adequate amounts of high quality scaup foods (e.g., freshwater shrimp and other invertebrates).

An earlier study conducted by researchers at Louisiana State University in 2001-02 suggested that scaup were actually losing weight when they migrated across the upper-Midwest, arriving in poorer condition in Manitoba, Canada, than they did just 20 years ago. A female scaup that arrives on the nesting grounds in poor condition will have to spend several weeks feeding to acquire enough food reserves to lay eggs, will lay fewer eggs than a healthy hen, will start nesting later than a healthy hen, and, consequently, will hatch her nest later, which will result in her ducklings having lower survival rates. In a nutshell, it appears that there may not be enough food in Midwest wetlands to enable scaup to return to the breeding grounds in good enough condition to nest successfully.

The lack of food is likely related to several factors. Our recent decade of abundant precipitation has caused many wetlands and shallow lakes to be unusually deep for several consecutive years. The deeper water has led to increased fish populations in many wetlands, particularly rough fish and minnows, which can cause wetlands and lakes to become overrun with algae. Excess nutrients, such a phosphorus and nitrogen, in runoff can also contribute to poorer water quality. Wetlands with poor water quality have few of the desirable plants and invertebrates needed by migrating scaup and other ducks.

  This spring, researchers will be placing colored nasal saddles (bill markers) on the bills of scaup captured on Pool 19 of the Mississippi River (near Keokuk) to see where and when these birds migrate across the Midwest and which wetlands they use. In addition, some of these marked scaup may be collected when they reach northern Manitoba to see how their body condition compares to when they were on Pool 19.

If you see any colored-marked scaup this spring, please note the date, time, color of bill marker, number on bill marker (if readable), sex of marked scaup (if determinable), location and number of birds in the flock and call, fax or e-mail the information to Louisiana State University. Instructions on how to report your observations as well as a report form can be found at: http://showcase.netins.net/web/iadnrcl/

Guy Zenner
Waterfowl Research Biologist
Iowa Dept. of Natural Resources
1203 N. Shore Drive,
Clear Lake, IA 50428