MANAGEMENT OF WETLANDS FOR SHOREBIRDS

PLANNING AHEAD FOR WILDLIFE SURVIVAL

The wetlands of Missouri provide habitat for waterfowl and many other groups of birds. Among these are the shorebirds, represented in Missouri by more than 40 migrant species. Shorebirds, including plovers, sandpipers, yellowlegs, etc., typically have long, somewhat flexible bills for picking and probing for food, and fairly long legs for wading in shallow water.

The food habits, feeding behavior and habitat requirements of shorebirds differ from those of migrant waterfowl and therefore warrant some special consideration in the design and management of wetland areas.

Management activity should be directed toward providing feeding and resting habitat during spring and fall migration rather than during the breeding season. Nesting habitat is somewhat less important since only four species regularly nest in Missouri. None of them four species require marshes or wetlands during the nesting or brood rearing period.

Site Selection and Development

Selection of the proper site for shorebird management is extremely important. Soil structure and availability of nearby water for flooding will have a great impact on the cost and eventual success of the management activities. The following criteria must be considered during the selection and development phase:

1. Sites on rich bottomland soils offer the greatest potential.
2. Alluvial sites containing areas of porous sands should be avoided.
3. Impoundments as small as 4 acres can be successfully managed for migrant shorebirds, however, larger areas can be managed more efficiently for shorebirds as well as provide habitat for migrant waterfowl.
4. Since optimum water depths for feeding shorebirds are from zero to 3 inches, considerably less than those used by waterfowl, the height of levees required will not be as great as those needed for waterfowl marshes.
5. The depth of water need only be sufficient to allow for the very gradual drawing down over the period from late March through the first week of June.
6. The drawdown rate must be based on the available water supply, the slope of the substrate, and rate of evapotranspiration. Care must be taken to ensure that water not be released too rapidly to create premature drying while migrants are still present.
7. A dependable source of water must be available for July impoundment flooding prior to the late summer and fall migration period. The water requirements may be met by pumping from a well, stream or nearby impoundment. A more suitable source would be from a higher reservoir.
8. Several types of water level control structures have been used. No matter what type is selected it must be able to affect changes as small as 1/2 inch and to allow for the rapid and total draining of the impoundment. A stop-log type control structure is best. Changes in water elevations are accomplished by the addition or removal of fitted boards of varying thicknesses.
9. The presence earthen hummocks (small islands) within an impoundment will enhance the area for shorebirds. These drier sites provide resting, preening, and feeding areas along the water edge.
10. Where feasible, large impoundments should be subdivided to increase management options. Different water depths will allow several management strategies, resulting in greater wildlife diversity. Interior levees should be constructed along contours at 6-inch contour intervals.

Shorebird Management

As in waterfowl management, the most important factors involved in shorebird management are proper timing of flooding or drawdown and maintenance or correct water depths. Most shorebirds prefer feeding areas which include shallow water up to three inches deep, exposed bare mudflats and some sites of short, sparse vegetation. Shorebirds migrate somewhat later in the spring and earlier in the fall than most waterfowl. The most effective spring management strategy is to maintain higher water levels throughout the winter, followed by gradual dewatering to expose just the highest areas of mud during the last week of March or the first week of April. Water levels should then be lowered very gradually at a rate calculated to ensure freshly exposed mud throughout the migration period. Shorebird migrations usually continue through the first week of June. This spring management sequence is quite compatible with waterfowl management since deeper water habits are available during peak duck migrations during late February or March. The shallow areas created by the initial drawdown are also attractive to most puddle ducks, such as northern shovelers and teal.

Management for the fall migration, which actually begins in mid-summer, involves a different strategy from that used during the spring. Most impoundments contain water prior to the spring period, while most areas are dry and covered with vegetation at the beginning of fall migration. Discing and shallow flooding in July will provide excellent shorebird feeding habitat. Discing reduces the dense summer vegetation, creates bare soil and exposes invertebrate prey items found below the surface. Prompt flooding to a depth of about three inches will create habitat that is preferred by migrant shorebirds. Burning will reduce vegetation also, but discing will have a longer lasting effect.

The major problem associated with fall shorebird management is maintaining high quality habitat throughout the length migration. Individuals of certain species, such as solitary and least sandpipers, arrive by the first week of July. Others such as long-billed dowitchers and dunlins persist until the water freezes, often in early November. Initiation of management to accommodate the early migrants can result in the undesirable revegetation of the flats and premature drying by the time later migrants arrive. In some situations, the problem of vegetation can be managed by briefly drawing down, Discing and reflooding. If two or more impoundments are available, one should be manipulated early in July while the other should be flooded during September.

Areas managed specifically for shorebirds are valuable to a wide range of other bird species. Shallow waters and mud habitats are used heavily by ducks, geese, herons, gulls, and terns.

Reference: Information and excerpts from Federal Aid Project W-13-R-33 and W-13-R-34, Shorebird Habitat and Phenology Studies in Missouri; and from moist soil management studies at the University of Missouri, Gaylord Memorial Laboratory, Puxico, Missouri.