Wildlife Habitat and Flyways
The wildlife habitats along the Mississippi River are important to a large number of migratory birds. Mature forested floodplain habitats in the Upper Mississippi, usually consisting of maples, cottonwoods and willows, are important to colonial-nesting birds such as herons, egrets, and double-crested cormorants. Farther south in the Lower Mississippi alluvial valley, bald cypress, gum, elm and various species of oaks provide important breeding, migration and winter habitat for numerous migratory birds. Neotropical migratory birds depend on these forests and brushy habitats for migration and breeding; studies have demonstrated the importance of this migration corridor to the species of migrants whose numbers are declining. The Mississippi River floodplain forest is also important to the bald eagle both for nesting and wintering habitat.
Most of the area within the floodplain of the river is wetland or converted wetland; this type of habitat is vital to many species of dabbling ducks for both migration and breeding. Both blue-winged teal and mallards nest on islands or in grasslands adjacent to the river, while wood ducks use tree cavities in the forests. Most importantly, the large, deep open pools of the river created by dams are vital to diving ducks, chiefly canvasback, redhead, lesser scaup and ring-necked ducks. Chief species using the Mississippi alluvial valley, which extends from southern Illinois to the coastal marshes of Louisiana, are the Mississippi valley and eastern prairie populations of Canada geese, snow geese, lesser white-fronted geese, and ducks such as gadwall, mallard, green-winged teal, American wigeon, American black duck, and northern pintail. Many other species of ducks use the river wetlands in lesser numbers.
The Mississippi River supports one of the most diverse fisheries in the world. One-third of all freshwater fish species in North America (195 species, live in the Mississippi River (Fremling et al. 1989). The diversity of the species generally increases from north to south. This diverse abundance of fish depends on many different aquatic habitat types including tailwaters, main channel, main channel border, side channel, and backwater habitat.
In three of the four pools in the study area (Pool 24, Pool 25 and Pool 26), three aquatic zones occur. The upper end of each pool most closely mirrors the river’s water level. In these areas, impoundment has had the least effect on the water levels. In this portion of the pools, marsh development is limited, and the pre-impoundment condition of deep sloughs and wooded islands are most common. As flows increase, the upper end of the pool becomes deeper until open river conditions exist. In the middle of each pool, impounded water is backed up over islands and floodplain wetland, spreading the river out over a large area. Water level remains relatively stable until open river conditions exist. Marsh development has occurred in the middle portion of the pools. Immediately above each dam (the lower pool), water was impounded to a depth that precluded most marsh development. At present, most of the lower pools’ area is deep, open water except when flows increase and water level decreases. As noted for each zone of the pool, water levels change when pool operation is manipulated by use of a hinge point.
Upland erosion and the sedimentation in downstream areas are major causes of reduced water quality and habitat destruction in most mid-western rivers and streams. Sedimentation in the backwaters of the Upper Mississippi River is a significant environmental problem.
Impounding the river has slowed the river current and increased silt deposition. Impounding the river has created backwaters and side channel habitat which benefits species like the largemouth bass, bluegill, and crappie that prefer still water. Riverine and sediment-tolerant species like the channel catfish, buffalo, drum and sturgeon still predominate in areas with current such as the main channel and main channel border.
In recent years the National Audubon Society through the Audubon Center at Riverlands has partnered with the Corps to study migratory birds in floodplain forests to help better understand their habitat needs and develop appropriate conservation goals. The Center's staff and volunteers have completed several years of on the ground forest bird monitoring using a rigorous standardized protocol for forest birds. The data collected from this effort and subsequent analysis has led to the development of a draft Upper Mississippi River Bottomland Forest Avian Stewardship Plan. The purpose of this planning effort is to develop a framework by which river habitat managers and supporting organizations can continue to study birds, use the data to analyze changes in bird populations and implement conservation measures to protect and improve bird habitat into the future on public lands.
DRAFT: Upper Mississippi River Bottomland Forest Avian Stewardship Plan