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Conservation Joint Venture Showing Early Signs of Success
CLEAR LAKE - For the third year in a row, the housing market for mallard ducks is looking up. Thanks to an ongoing, joint venture agreement between Iowa DNR, the Delta Waterfowl Foundation, and Waterfowl Association of Iowa, migrating mallards will find a noticeable increase in the availability of safe nesting sites as they arrive in Iowa later this month. According to DNR Waterfowl Technician and project coordinator, Al Hancock, the continuing conservation partnership has a goal of installing 500 artificial mallard nesting structures on Iowa wetlands over four years. Known as Delta Hen Houses, the structures are three-foot-long, 18-inch diameter wire cylinders covered and lined with natural nesting material. When installed over water, the structures provide safe haven from egg eating predators such as skunks, mink and raccoons. The joint effort represents the first Hen House Super-Site ever attempted in Iowa. During its first two years, the project focused on public marshlands surrounding Clear Lake in north central Iowa. This year, the project is being expanded to include wetlands in northwestern Iowa. By the time marshes open this spring, at least 300 nest cylinders should be in place and ready for use, says Hancock. Although the nest structure project is still under construction, preliminary results are encouraging. During the project's first year [2008], the only nesting cylinders to receive use were located at the Union Hills Wildlife Area. Structures on all other areas were apparently ignored by breeding hens. During the 2009 nesting season, the number of mallards attracted to the sites doubled at Union Hills, and nesting cylinders received at least some duck use on nearly all of the 17 public wetland areas where nests were installed. First time use is a critical step, and Hancock feels the stage is set for continued growth. By examining the behavior of banded mallards, biologists have discovered that successful hens will return to the same nesting cylinders year after year. As those hens continue to produce broods of ducklings, more and more [surviving] females return to the same area. By tagging ducklings in the nest, scientists have also learned that mallards hatched in nest cylinders are extremely prone to use the same type of structures as adults. As more and more adult females return each spring, project success grows. In a previous Iowa trial, artificial nesting cylinders used by mallard ducks enjoyed 70 to 87 percent hatching success. By contrast, around 80 percent of the mallard nests initiated [on the ground] in traditional upland areas were lost to predators. To maintain a stable population, mallards need a nesting success rate of at least 15 percent.
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