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Locating and Managing Peninsulas for Nesting Ducks

Location Factors for Peninsulas

Peninsula locations can be obtained by examining aerial photography or National Wetlands Inventory data or by querying local resource managers. Aerial photographs can be examined at county U.S. Department of Agriculture (USDA), Agriculture Stabilization and Conservation Service (ASCS) offices or purchased from USDA-ASCS, P.O. Box 30010, Salt Lake City, UT 84130-0010. National Wetlands Inventory maps can be obtained from the U.S. Geological Survey, Box 25046, Stop 504, DFC, Denver, CO 80225.

Aerial photographs of Alberta, Canada can be obtained at Maps Alberta, Land Information Services Division, 2nd Floor, North Petroleum Plaza, 9945 - 108 Street, Edmonton, AB, Canada T5K 2G6. Aerial photographs of Manitoba and Saskatchewan can be ordered from the Surveys and Mapping Branch, 1007 Century Street, Winnipeg, MB, Canada R3H 0W4 and at the Map and Air Photo Distribution Center, 1st Floor, 2045 Broad Street, Regina, SK Canada S4P 3V7.

Shoreline Vegetation

Shorelines of managed peninsulas should be free of tall emergent vegetation. Tall emergent plants such as cattails and bulrush provide attractive foraging habitat for raccoon and mink, but reduced habitat for loafing and feeding duck pairs. Shorelines preferred by breeding pairs have bare soil or a covering of low grasses and sedges. Alkaline wetlands usually produce the most suitable shorelines because tall, emergent plants do not grow in alkaline soil. Wetlands with extensive blocks of emergent cover such as cattails and bulrush should be avoided.

Wetland Type

Peninsulas located at large, alkaline, semipermanent wetlands are the most suitable for management. Alkaline wetlands that are preferred as construction sites are classified as brackish, subsaline, and saline by Stewart and Kantrud (1971) or mesosaline, polysaline, eusaline, and hypersaline by Cowardin et al. (1979). A characteristic plant of alkaline wetlands is alkali bulrush, but these wetlands often have few emergent plants. Alkaline wetlands probably provide superior conditions for nesting ducks because these wetlands furnish poor food and cover for raccoon and mink. Peninsulas located at large, fresh, semipermanent or permanent wetlands with little emergent cover are secondary choices for management.

Peninsulas at seasonal or temporary wetlands should not be managed. These wetlands are often dry and predator barriers may not function effectively in most years. Also, peninsulas along the shorelines of large reservoirs generally provide poor management sites because fluctuating water levels and severe wave action regularly damage the predator barriers. Acceptable peninsula management locations may, however, occur on small, stable reservoirs.

Photo of predator barrier next to an alkaline wetland.
Alkaline wetlands usually produce the most suitable shorelines because tall, emergent plants do not grow in alkaline soil. (photo by USFWS)

Wetland Complexes

To be effective, peninsulas managed for nesting ducks should be located within a good network of surrounding wetlands. At least 40 wetland basins or 80 wetland acres (32 ha) should be located within 1 mile (1.6 km) of the managed peninsula to supply food and cover for breeding pairs and broods. Mallards, gadwalls, and northern pintails have large home ranges and will move 1 or 2 miles from wetlands to nest on managed peninsulas. However, blue-winged teal have small home ranges and will move one-half mile or less between wetlands and peninsulas to nest.

Wetland complexes with temporary, seasonal, and semipermanent wetlands supply food and space for duck pairs in spring and for hens and their broods in summer. Diverse wetland complexes are particularly important to ducks using peninsulas at highly alkaline wetlands or permanent, fresh wetlands which may lack adequate food and cover.

Maps showing the potential waterfowl breeding pair values for each 40 acre unit of land are being created for eastern North Dakota and South Dakota and northeastern Montana. The procedure uses Geographical Information System techniques to combine data on wetlands, duck pair and wetland relationships, and breeding duck home range for five upland nesting species. The maps are available at the Habitat and Population Evaluation Team, 1500 East Capitol Drive, Bismarck, North Dakota 58501-2096.

Aerial photo of wetland complex.
To be successful, nesting peninsulas, like nesting islands, must be close to good wetland complexes that support waterfowl breeding pairs and broods. A good wetland complex would typically include 40 or more basins within 1 mile of the peninsula. (photo by Northern Prairie Wildlife Research Center)

Size and Spacing

Size and spacing are important considerations in peninsula management. It is usually not cost-effective to construct predator barriers on peninsulas smaller than 3.5 acres. Small peninsulas generally attract few nesting hens, and they are nearly as expensive to manage as large peninsulas.

Managed peninsulas should be spaced at least 1 mile from each other and from other intensively managed nesting habitats. Separating intensively managed nesting sites by a mile or more makes each accessible to different breeding pairs and increases the chance of having more nests. However, intensively managed sites should not be so widely separated that they cannot easily be visited and maintained.

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