Locating and Managing Peninsulas for Nesting Ducks

Graphic: Waterfowl flying away from predator barrier.

John T. Lokemoen and Terry A. Messmer
U.S. Fish and Wildlife Service
The Berryman Institute, Logan, Utah

1994

The purpose of this extension bulletin is to guide the management of nesting ducks on peninsulas on public and private lands. Managing peninsulas for ducks is a relatively new strategy that was developed in the grassland region of western North America. Information contained in this bulletin is primarily from studies conducted by biologists working at the Northern Prairie Wildlife Research Center, Jamestown, North Dakota.

This resource is based on the following source (Northern Prairie Publication 0917):

Lokemoen, John T. and Terry A. Messmer.  1994.  Locating and managing peninsulas 
     for nesting ducks.  U.S. Fish and Wildlife Service, Branch of Extension and
     Publications, Arlington, VA and The Berryman Institute, Logan, UT.  18pp.

This resource should be cited as:

Lokemoen, John T. and Terry A. Messmer.  1994.  Locating and managing peninsulas 
     for nesting ducks.  U.S. Fish and Wildlife Service, Branch of Extension and
     Publications, Arlington, VA and The Berryman Institute, Logan, UT.  
     Jamestown, ND: Northern Prairie Wildlife Research Center Online.
     http://www.npwrc.usgs.gov/resource/birds/penin/index.htm (Version 12MAY03).

Introduction
- Common Nesting Species
- Management Options and Costs
Location Factors for Peninsulas
- Shoreline Vegetation
- Wetland Type
- Wetland Complexes
- Size and Spacing
Construction Guidelines for Predator Barriers
- Electric Fences
- Water-Filled Moats
Management of Peninsulas
- Seeding Grass-Legume Nesting Cover
- Removing Tall Shrubs and Trees
- Livestock and Fencing
- Managing Predators
Monitoring Peninsulas
- Maintaining Permanent Records
- Monitoring Predators
- Monitoring Nesting
Required Permits
- Federal Permits
- State, Province, and Local Permits
Suggested Reading

Appendices

Appendix A -- Manufacturers and Distributors of Electric Fence Materials
Appendix B -- Sources for Grass and Legume Seeds
Appendix C -- Peninsula Survey Form
Appendix D -- Agencies Providing Guidance and Grant Permits

Figures

Figure 1 -- Area of peninsula management in the Prairie Pothole Region of the United States and Canada.
Figure 2 -- The three styles of electric fences for pointed and blunt peninsulas.
Figure 3 -- Detailed illustration of the standard electric peninsula fence.
Figure 4 -- Illustration of a quick-kill body trap set in a box.
Figure 5 -- Form for recording physical, predator, and bird nest data and success at peninsulas.

Introduction

Production of upland-nesting ducks in the northern prairie region of North America is severely limited by high levels of predation. Studies conducted in this region during the last several decades revealed nest success rates of only 10 to 20%. Much of the predation is caused by medium-sized mammals including the red fox, striped skunk, raccoon, badger, and mink. These predators mainly destroy duck eggs but some species also take ducklings and incubating hens.

Many current management strategies seek to increase duck nest success by separating the nest from the predator. One way to provide this separation for upland-nesting ducks in the northern prairies is by managing peninsulas. Peninsulas in this paper are defined as projections of land into water, connected to the mainland at the base by an isthmus. Peninsulas provide good management sites because they are naturally attractive to nesting ducks and mammalian predator access is limited to a narrow isthmus. Predation can be greatly reduced at peninsulas by placing barriers on the isthmuses and removing predators that gain access.

Peninsula management has been most widely applied in the Prairie Pothole Region and to a lesser extent in the prairies and plains to the west (Figure 1). Managed peninsulas are usually natural parcels of land located in large wetlands. A variety of peninsula types can be managed including long narrow ones that project nearly across the wetland and broad ones that extend only a short distance into the wetland.

Duck nest success in the northern prairies averaged over 50% on peninsulas managed with predator barriers and predator control. On average, each managed peninsula contained 1.3 nests/acre (3.2 nests/ha). Duck nest success on unmanaged peninsulas was usually less than 15% with about 0.3 nests/acre (0.7 nests/ha).

Map of the United States and Canada with shaded portion showing the Prairie Pothole Region.

Figure 1. Peninsula management has been primarily applied in the Prairie Pothole Region of the United States and Canada and secondarily in the plains region to the west.

Common Nesting Species

Mallard, gadwall, and blue-winged teal are the primary nesting species attracted to managed peninsulas. These 3 species together compose about 75% of the ducks nesting on peninsulas. Northern pintail and lesser scaup each compose about another 10% of the nesting population. Although Canada geese, shorebirds, and colonial water birds seek islands as nesting sites they seldom nest on peninsulas.

Mallards, gadwalls, and blue-winged teal are the primary nesting species attracted to managed peninsulas. (photo by USFWS)

Management Options and Costs

Before initiating peninsula management, managers should visit each potential site, catalog its attributes, and determine its value for producing ducks (see section on Monitoring Peninsulas). The value of each peninsula for nesting ducks can be related to management costs in order to obtain the benefit-cost relationships of various sites. Although economic and engineering concerns must receive strong attention in the planning process, biological concerns must be given primary consideration. During the peninsula inventory process, managers should also consider evaluating island-nesting sites concurrently (Lokemoen and Messmer, 1993). Ultimately, the most cost-effective waterfowl management projects should be identified and developed first.

Predator barriers normally applied at peninsulas include electric fences and water-filled moats. Electric fences are the most cost-effective barrier because heavy equipment is not required for construction. In North Dakota, in the 1980s, the mean capital cost of constructing electric fences across peninsulas was $7,600 or about $7/foot. This compares to a mean capital cost of $207,000 for moats or about $100/foot. The cost of each fledged duck, including capital, maintenance, and predator trapping, was estimated at $12 for fenced sites and $62 for moated sites.

Photo of predator barrier with electric fence extending into a wetland.

Electric fences are the most cost-effective predator barrier on peninsulas, because heavy equipment is not required for construction. (photo by USFWS)

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.

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.

Construction Guidelines for Predator Barriers

Electric Fences

Most electric fences used as predator barriers consist of a wire mesh fortified with electric wires to prevent predators from moving over, under, or through the fence. Electric fences have been constructed in three basic configurations depending mainly on the shape and location of the peninsula (Figure 2). On peninsulas with narrow isthmuses, the fence is built straight across the isthmus. On peninsulas that terminate near the far shore (closer than 200 feet), one fence is built straight across the isthmus and another fence is built straight across the tip. On peninsulas with broad isthmuses the fence must extend in two directions from a corner.

Figure 2: Illustration showing three types of fence barriers for different types of peninsulas.

Figure 2. The three styles of electric fences showing a pointed peninsula with a single fence barrier, a pointed peninsula with two fence barriers, and a blunt peninsula with a fence that extends in two directions.

The ends of all electric fences should extend about 50 feet into open water to a depth of at least 1 foot (0.305 m) based on average wetland levels. If electric fences have to project 100 feet or more into the wetland to reach a water depth of at least 1 foot, the peninsula probably cannot be managed cost-effectively.

Most electric fences have a permanent dry land portion and an attached but removable wetland segment (Figure 3). Wire mesh on dry land portions of electric fences should extend from 1 foot below ground to 5.5 feet above ground. In wetlands, the wire mesh should extend from the pond bottom to 5.5 feet above the bottom. The dry land portion of an electric fence normally includes two kinds of wire mesh. The upper mesh should be a galvanized wire such as poultry netting (1-inch or 2.54-cm mesh, 18-gauge), welded-wire fabric (1 × 2-inch mesh, 18-gauge), or horse-fence (2 × 2-inch mesh, 16 gauge). The upper mesh serves as a ground for the energized wires so it must be connected to an earth ground. Vinyl-clad wire mesh is often used for the lower 2 feet, including that below ground, to prevent rusting. The 2 wire meshes are woven together with stainless steel wire or fastened together with hog-rings.

Figure 3: Diagram of standard electric peninsula fence.

Figure 3. Detailed illustration of the standard electric peninsula fence showing the dry land portion, the wetland portion, and the electrical connections to the solar-powered energizer. Measurements are in inches.

The top 1 foot of electric fences should lean towards the base of the peninsula at a 45° angle. If coyotes are not present in the region, a overhang may not be needed and a fence height of 4.5 to 5 feet would be sufficient. If there is a threat of fire, vegetation 5-10 feet on either side of the fences should be mowed to prevent flames from scorching the wires. Scorched wires will soon rust and deteriorate.

Three energized wires (12.5 gauge) are attached to the side of the electric fences facing the base of the peninsula. Two energized wires are placed 4 feet above ground and 2.5 inches and 5 inches from the wire mesh. The wires are held in place by fiberglass rods that are driven into the wooden posts and by insulators that are nailed to the wooden posts or attached by spring clips to the wire mesh. The third energized wire is placed 2.5 inches above the top of the wire mesh. This top wire is connected to insulators that are attached to the rod that supports the 45° overhang. All wire mesh and electrified wires must be stretched tightly.

A small, high-voltage energizer, powered by a 12 volt deep-cycle marine battery, is used to electrify the wires. The battery charge is readily maintained through the use of a solar charger.

To reduce water and ice damage to segments of the electric fences in the wetland, use commercially available "cattle panels" (16 × 4.25-feet, 4 gauge). Each panel should be covered with 1-inch wire mesh, and an energized wire placed near the top. The energized wire is attached to the wire mesh on each panel by a spring clip insulator. The panels can be fastened together with hog-rings or stainless steel wire and held upright with fence posts that are driven into the wetland bottom. The panels should be placed in the wetland each spring after the ice melts and removed after the nesting season before the lake freezes.

Fences should be checked regularly for electrical malfunctions and structural damage. Materials for electric fences are available at lumber companies, farm supply stores, and from national distributors (Appendix A). Additional details concerning electric fence construction and operation is found in a manual prepared by Rondeau and Piehl (1989).

Water-filled Moats

Water-filled moats can also be used as effective predator barriers to reduce access of certain mammalian species to peninsulas. Moats should have 3:1 side slopes with a water barrier that is 200 feet or more wide and at least 3 feet deep, based on average wetland levels. Moats are expensive to build and, therefore, best suited to peninsulas with narrow isthmuses. Earth removed from the excavations can sometimes be used to increase the peninsula area or to create nesting islands.

Water-filled moats also provide effective predator barriers. In many cases the excavated soils can be used to extend the peninsula. (photo by Harold Umber, North Dakota Game and Fish Department)

Management of Peninsulas

The manipulation of nesting cover and control of mammalian predators are important considerations at peninsulas managed for nesting ducks. The primary duck species nesting on peninsulas prefer tall grass and forb (1-to 2-feet) and low shrub (less than 4 feet) cover. Hens generally avoid tall shrubs (more than 4 feet high) and trees for nesting. Peninsulas lacking adequate nesting cover can be improved by rejuvenating or protecting existing vegetation or by seeding new plants.

Seeding Grass-Legume Nesting Cover

Good nesting cover can be provided at peninsulas by seeding proper mixtures of tall, introduced grasses and legumes. Grass-legume mixtures should be seeded into a firm soil substrate. Prior to seeding, existing plants at the site should be eliminated by repeated cultivations or use of wide-spectrum herbicides. Grass-legume seedings are best completed using small grain drills or no-till drills. Seeding should be completed in early spring, late fall after plant growth has stopped, or winter after peninsula construction. Suitable grass-legume nesting cover includes intermediate wheatgrass, tall wheatgrass, and smooth brome mixed with alfalfa and small amounts of sweetclover. Introduced grass and legume seeds are widely available at seed dealers distributed throughout the western United States and Canada (Appendix B). For detailed advice regarding grass-legume seedings, refer to Duebbert et al. (1981).

The vigor and attractiveness of planted grass-legume cover vary between years but tends to decline over time. Plant vigor can be restored for several years by cultivating existing stands. Prior to the cultivation treatments, remove the existing plants using fire or mowing. Cultivation should completely disturb the soil and plant roots to a depth of 4 to 6 inches. The treatment should be conducted in spring or late fall. Revegetation will occur naturally on the cultivated area from roots or dormant seeds in the soil.

Removing Tall Shrubs and Trees

Tall shrubs such as northern hawthorn and wild plum, and trees such as box elder are generally avoided by nesting ducks because the foliage shades out low ground cover. Tall shrubs and trees also provide perching and nesting sites for avian predators. Tall shrubs and trees should be removed from managed peninsulas by cutting and then spraying ensuing sprouts with an approved herbicide.

Branches and wood debris that remain after shrubs and trees have been cut down should be stacked in piles and burned. However, fire should not be allowed to extend throughout the peninsula. Burning is not recommended for peninsulas as fire will temporarily eliminate all nesting cover and permanently reduce the important forb and low shrub cover component. Burning is advised only at peninsulas that are to be reseeded or to eliminate piles of dead shrubs and trees.

Livestock and Fencing

Nesting cover that has been reduced on peninsulas by grazing can be restored by excluding livestock. The electric fence or moat will help exclude cattle but additional fencing may be required. Fall or perhaps winter grazing may be of most concern because cattle can reach peninsulas by crossing through wetlands when they are shallow, dry, or frozen. Fall grazing is detrimental because vegetation that provides nesting cover for the next year is removed. Additional fencing or a change in the grazing practices may be required in these situations. Electric fences should remain energized when livestock are present to prevent damage to the wire mesh and posts by rubbing.

Managing Predators

Mammalian predators that gain access to managed peninsulas should be removed by trapping. It is extremely important to employ a skilled trapper who is able to effectively remove all species of mammalian predators. Trapping can be accomplished by using snares, live-traps, quick-kill body traps set in boxes (Figure 4) or, if necessary, leg-hold traps. Trapping should extend from early April, when wetlands become ice-free, until mid-July, when nesting is essentially completed.

Generally, traps should be set only on the managed peninsula and not on the adjacent mainland or shoreline. Traps set on adjacent lands will capture many animals that are not destroying nests on the managed peninsula. Traps should be dispersed throughout the peninsula habitats. Productive trapping sites include shorelines, rock piles, dens, and patches of tall, emergent plants.

Avian predators have not been a primary concern on managed peninsulas in North and South Dakota and Montana. However, in some areas, American crows and black-billed magpies may take duck eggs and large raptors may kill nesting hens. Avian predation may be reduced by removing tall shrubs and trees from the managed peninsulas and the adjacent shoreline.

Figure 4: Diagram of quick-kill body trap box.

Figure 4. Illustration of a quick-kill body trap set in a box. The rear of the box is closed by 1/2-inch wire mesh to prevent access but allows the animal to see inside. Dimensions of the box are 24" × 12" × 12".

Monitoring Peninsulas

Maintaining Permanent Records

The management potential of peninsulas for nesting ducks should be determined by a field examination. Information acquired during field examinations should be permanently recorded for use in future management decisions (Figure 5, Appendix C). Each record should include a peninsula name or other identifier, location, habitat description, and information on predator activity and duck use. Many characteristics such as wetland size, peninsula size, wetland type, and wetland number and area can be measured from aerial photographs or National Wetlands Inventory data. Information can be stored on data sheets or as computer accessible files. It is usually helpful to maintain location and cover maps of the sites on file for future use.

Universal Transverse Mercator (UTM) coordinates, taken at the center of the peninsula, can be used for both the location and the identifier. UTM coordinates can be determined on 1:24,000 maps (7.5 minute series) and 1:250,000 maps available from the U.S. Geological Survey, Denver, CO 80225. In Canada, the UTM coordinates are on 1:50,000 maps available from Energy, Mines & Resources, Ottawa, Ontario, Canada K1A 0E9. UTM coordinates should be measured to the nearest 10 meters (32.8 feet) on all map scales.

Figure 5. Form for recording physical data, predator information, and bird nest numbers and success at peninsulas.

Monitoring Predators

Managed peninsulas should be surveyed for the presence of predators each spring after the ice melts and before trapping begins. Knowledge of the predator species activity at each peninsula is an important guide to the intensity of the predator control required. Mammalian predators are often difficult to observe but their presence can usually be detected by searching for tracks along shorelines and other bare-soil areas. Active dens or fresh scats also indicate the presence of certain predator species. Evidence of predators should be noted on the Peninsula Survey Form (Appendix C).

If bare soil or shorelines are absent, track plots can be constructed by maintaining a 3 feet × 6 feet area free of vegetation. Loamy soil makes the most suitable substrate for identifying animal tracks. During each visit, track plots should be examined for predator sign and then raked clean.

Monitoring Nesting

The duck nesting effort and nest success on managed peninsulas should be appraised every few years by conducting nest surveys. To obtain comparable data, all nest surveys should be conducted in a similar manner during the middle of the nesting season. In the northern plains, a relatively good estimate of nesting effort and nest success can usually be obtained from 2 nest searches. The first search should be conducted in May and the second search should be done 3-4 weeks later in June.

Nest searches should be conducted by 2 or more people pulling a weighted rope over all of the available nesting cover. After a nest is found the location should be marked by placing a willow stake or wire survey flag near the nest bowl (normally 13 feet or 4 m north). The nest identification number should be written on the stake or flag with permanent ink. The nest location should be noted on a map or aerial photograph. The waterfowl species, number of eggs, and incubation stage should be recorded on a nest card; one of which is completed for each nest.

Nest fate should be checked about 2 weeks after the first nest search, during the second nest search, and about 3 weeks after the second nest search when all nest histories are completed. All nests are seldom found, so the Mayfield estimate of nest success should be used (Johnson and Shaffer 1990). A summary of duck nesting data should be recorded on the Peninsula Survey Form. See Klett et al. (1986) for a complete description of nest study techniques.

Required Permits

Federal Permits

A federal permit is not required for the construction of electric fences in the United States or Canada. A U.S. Army Corps of Engineers, Section 404 permit is required for moat construction and placement of fill in a wetland in the United States but no federal permit is needed in Canada. Section 404 permits can be obtained at the nearest Corps of Engineers Field Office, but must be requested at least 3 months prior to the proposed construction date. The permit process requires each applicant to complete a 2-page application form (ENG 4345). The form should be fully completed including a vicinity map, construction plans, and scale drawing that provides elevation and cross-section views. Once the application is completed and signed, it must be returned to the field office.

If the project changes significantly after a permit has been granted, a new application must be submitted and a new permit obtained. Peninsula construction projects would generally fall under a non-commercial activity, for which the application fee is currently $10.00. For most peninsula construction, Section 404 permits are granted under a regional or nationwide authorization.

Location of U.S. Army Corps of Engineers offices in the Missouri River drainage can be obtained at 215 N 17th Street, Omaha, NE 68102-4978 and for the eastern Dakotas, Minnesota, and Iowa at 180 E Kellogg Boulevard, St. Paul, MN 55101-1479. Permit information for California, Nevada, Utah, and Arizona can be acquired at 1325 J Street, Sacramento, CA 95814-2922 and information for eastern Washington, Oregon, and Idaho at Building 602, City-County Airport, Walla Walla, WA 99362-9265.

A U.S. Fish and Wildlife Service permit may be needed prior to construction when a change will be made to a wetland where there is a wildlife easement. Contact the U.S. Fish and Wildlife Service at P. O. Box 25486, DFC, Denver, CO 80225 if you are in the western portion of the prairie pothole region. Contact the Service at the Federal Building, Fort Snelling, Twin Cities, MN 55111 if you are in Minnesota or Iowa; at Box 1306, Albuquerque, NM 87103 if you are in Arizona, New Mexico, or Texas; or at Lloyd 500 Building, Suite 1692, 500 NE Multnomah Street, Portland, OR 97232 if you are in Idaho, Washington, Oregon, California, or Nevada.

State, Province, and Local Permits

In addition to the requirement for Federal Section 404 permits, local, state, or provincial permits may be needed for moat construction. The requirements for such permits vary by locality. To find out what permits may be required in your area, contact the appropriate resource agency (Appendix D). Also, local, state, or provincial permits may be needed for removing predators outside of the regular trapping season.