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Ecology and Management of Islands, Peninsulas and Structures for Nesting Waterfowl

Evaluation of Waterfowl Habitat Structures in Southwestern Montana

James W. Roscoe
Bureau of Land Management
Dillon, Montana 59725

Various structures have been used in the Centennial Valley of southwestern Montana to improve habitat suitability for duck and goose production on approximately 15,000 acres of public wetlands subject to livestock grazing. Pothole blasting using ANFO created 115 potholes on four grazing allotments and one unleased tract, with a goal of providing open water areas in dense monotypic stands of Carex spp., and in some cases, also providing stock water. Ponds were clustered to provide maximum diversity. Duck breeding pair use on the 120-acre unleased tract increased from fewer than five pairs to 175 pairs within two years. Greatest response was from mallard (Anas platyrhynchos), blue-winged teal (Anas discors), pintail (Anas acuta), and shoveler (Spatula clypeata). Actual production was not determined. Effectiveness of potholes on grazed allotments was limited by livestock trampling, slow revegetation even after seeding, and small pond size (less than 1000 square feet surface area). Blasting cutoffs on peninsulas and oxbows has been the most effective method for providing secure nest sites with good residual cover. Forty-five raised nesting platforms for Canada geese (Branta canadensis) were erected on the Red Rock River and Madison River in 1981, 1984, and 1985 to provide secure nesting sites where residual nesting cover was lacking. Occupancy of structures on the Red Rock River has averaged 70% since 1985, producing 4.4 fledglings per structure. Structures on the Madison River, where natural nest sites are available, have been unused by geese. Nest platforms have also been used for nesting or roosting by mallards, great blue herons (Ardea herodias), Swainson's hawk (Buteo swainsoni) and peregrine falcon (Falco peregrinus). Islands constructed in Lima Reservoir in 1977 have been unsuccessful at providing waterfowl nesting habitat due to construction with sodic soils which are extremely vulnerable to erosion, poor establishment of nesting cover, and subsequent colonization by gulls and cormorants. Areawide, improved grazing management through system implementation and fencing has been more effective at enhancing wetland suitability for waterfowl production than has the development of artificial structures.

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