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Wetland Symposium

Waterfowl Use of Restored Wetlands in Iowa


GUY G. ZENNER AND THEODORE G. LAGRANGE

Iowa Department of Natural Resources, Fish and Wildlife Station, 1203 North Shore Drive, Clear Lake, IA 50428

From 1987-92, the Iowa Department of Natural Resources, U.S. Fish and Wildlife Service, county conservation boards, and private conservation organizations worked together to restore 893 wetlands totaling 1,474 ha in Iowa's Prairie Pothole Region. Most restored wetlands were on Conservation Reserve Program (CRP) lands or land acquired under the Prairie Pothole Joint Venture Program. To evaluate waterfowl use of these restored wetlands, breeding-pair ground counts were conducted in May on 135 restored and 65 existing wetlands in 1989 and on 228 restored and 158 existing wetlands in 1990-92. Nearly all existing wetlands were on wildlife management areas (WMA's). Analysis was restricted to palustrine emergent seasonally and semipermanently flooded wetlands less than eight ha. Blue-winged teal (Anas discors) and mallards (Anas platyrhynchos) composed 41 and 15% of the pairs on restored wetlands, respectively, and 43 and 22% on existing wetlands, respectively. Preliminary analysis indicated breeding pair densities (pairs/ha) for mallards, blue-winged teal, and total ducks on restored wetlands averaged 1.5, 3.0, and 5.9, respectively, during 1989-92. In comparison, breeding pair densities for mallards, blue-winged teal, and total ducks on existing wetlands averaged 0.7, 2.0, and 3.7, respectively, during 1989-92. Canada goose (Branta canadensis maxima) pair densities on restored and existing wetlands averaged 0.7 and 1.0, respectively, during 1989-92.

Nest success of ducks using associated grasslands during 1989-92 was determined using standard waterfowl nest searching and monitoring techniques developed at Northern Prairie Wildlife Research Center, Jamestown, ND. Preliminary analysis indicated Mayfield nest success rates for mallards, blue-winged teal, and total ducks on CRP grasslands associated with restored wetlands were 16 (n = 45), 22 (n = 138), and 20% (n = 199), respectively. In comparison, Mayfield nest success rates for mallards, blue-winged teal and all ducks on WMA grasslands associated with existing wetlands were 18 (n = 49), 15 (n = 133), and 17% (n = 191), respectively. To further evaluate waterfowl use of restored wetlands, brood surveys were conducted in July on a sample of restored wetlands in 1991 and 1992. The 58 restored wetlands surveyed were predominantly open water so broods could be easily observed during morning and evening hours. Observations indicated 1.2 broods/ha both years with 8.2 and 7.7 ducklings/ha in 1991 and 1992, respectively. Results indicate that restored wetlands were rapidly colonized by a variety of breeding waterfowl, waterfowl pair densities were higher on restored wetlands than on existing wetlands, duck nest success in associated grasslands was comparable to other parts of the Prairie Pothole Region, and brood use of restored wetlands was high.


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