Important Bird Areas

Active Delta (Mississippi River Birdsfoot Delta)

Louisiana

The Active Delta IBA is located in the active Mississippi River birdsfoot delta. The IBA includes the lands comprising Pass-a-Loutre WMA, Delta NWR, land northeast of Delta NWR and north of the Mississippi River, and the state waters surrounding the public lands. Due to the influence of the Mississippi River, the area supports a large fresh marsh system with brackish to saline marshes along its edges which border the Gulf of Mexico and Breton Sound. Vegetation is primarily Phragmites spp. with large sedimentary alluvial fans dominated by Sagittaria spp. and Scirpus spp. The area is extremely important for wintering waterfowl, wading birds, secretive marsh birds, and shorebirds. The area also provides important nesting and brood-rearing habitat for Mottled Ducks, secretive marsh birds and wading birds. Shrub dominated spoil banks and willow dominated areas provide important migratory stopover habitat for many Neotropical migrants.

Ornithological Summary

Threatened and endangered species on the IBA include American Alligator, Brown Pelican, Arctic Peregrine Falcon, and Piping Plover.

The Active Delta (Mississippi River Delta) IBA is extremely important for wintering waterfowl, wading birds, secretive marsh birds, and shorebirds. It provides important nesting and brood rearing habitat for mottled ducks, secretive marsh birds and wading birds. Shrub-dominated spoil banks and willow-dominated areas provide important migratory stopover habitat for many Neotropical migrants.

The freshwater marsh in particular holds high densities of King Rails, though no quantitative data for King Rails exist. Western Sandpiper, Least Sandpiper, and Dunlin winter on the IBA. One hundred and seventy-five species of birds were detected during two seasons of transect counts on Delta NWR and Pass a Loutre WMA, during only a few months each year. Tens of thousands of wintering waterfowl utilize the delta?s rich food resources. There are numerous wading birds in the marshes, and thousands of shorebirds are found on tidal mudflats and deltaic splays. Commonly observed are greater and lesser yellowlegs, long-billed dowitchers, dunlins, Western sandpipers, Wilson?s plovers, killdeer and willets.

Raptors are also common on the IBA, with commonly observed species including American Kestrels, Northern Harriers, Red-tailed Hawks, Turkey Vultures, and Cooper?s Hawks. Ospreys are commonly seen in the winter at the site.

Conservation Issues

The major threats to the Active Delta IBA are loss of land building sediment due to the channelization of the Mississippi River and the armoring of the Mississippi River banks with levees. These activities prevent overbank flooding and deposition of sediments that gave rise to the marsh, and would continue to build marsh. The disruption of the natural river flow turns natural events, such as hurricanes and subsidence, into forces that further destroy the marsh. Subsidence, the natural settling of marsh vegetation, to consume marsh. While hurricanes and storms are natural erosional factors for these coastal marshes, their impact is now not being mitigated by the rebuilding of marsh through overbank flooding, and the impact may be worsening in intensity and frequency due to global climate change. During hurricanes, such as Hurricane Katrina in 2005, marsh is inundated with salt water, torn up by storm surge, and impacted by oil and gas spills and the deposition of debris. Marsh and beach are also eroded, and trees are toppled by the hurricane winds. The marsh, with further fresh water and sediment inputs, would recover from these impacts over time.

Dredging of canals, primarily for oil and gas exploration, also allows salt-water intrusion into the marshes, further degrading the marsh.

For clarity, natural and human-created breaks in levees, otherwise known as freshwater diversions, are beneficial in diverting and slowing water flow and helping to rebuild marsh habitat.

Ownership

U.S. Fish and Wildlife Service owns Delta National Wildlife Refuge, while Louisiana Department of Wildlife and Fisheries owns Pass-a-Loutre Wildlife Management area. There are also various private landowners.

Habitat

Over 70 percent of this site is open water, which is used for feeding by wintering waterfowl and some seabirds. The land area is composed of 2 primary vegetation types. The majority of the vegetated area is composed of fresh to brackish marsh dominated by Phragmites species. The predominant plants in the fresh marsh zone include delta duck potato (Saggitaria platyphylla), elephant ear (Colocasia antiquorum), wild millet (Echinocloa crusgalli), delta three-square (Scirpus deltarum), and roseau cane (Phragmites spp.) The other major vegetation type, of more importance to wildlife, consists of sedimentary alluvial fans dominated by Sagittaria spp. and Scirpus spp. There are also beaches used by wintering shorebirds.

Land Use

The public lands are maintained as wildlands managed by the Louisiana Department of Wildlife and Fisheries and U.S. Fish and Wildlife Service. Hunting, fishing, some bird-watching, boating, and environmental restoration are also pursued on the public lands. Private lands are used for hunting, fishing, and limited cattle grazing. Oil and gas development is present on all areas in substantial numbers.

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