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Mississippi Alluvial Valley
(Area - 11,461,500 ha)
Executive Summary |
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Location and physiography - This area includes the floodplain of
the Mississippi River that cuts into the Gulf Coastal Plain, extending north to and including the
delta at the confluence of the Mississippi and Ohio Rivers and south toward the Gulf of Mexico.
The Alluvial Valley includes most of eastern Louisiana, eastern Arkansas, northwest Mississippi,
small portions of west Tennessee and Kentucky, the bootheel of Missouri, and the Cache River
lowlands of Illinois. Nonforested marsh in southern portions of the floodplain is included in the
Coastal Prairie physiographic area. Water shaped this land. The ridges and swales, levees,
oxbows, and terraces of the Valley all resulted from meanderings and floods of the Mississippi
River. Small changes in elevation determine how wet a site is, the plant community that grows
there, and habitat conditions for birds.
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Priority
Bird Populations and Habitats
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Bottomland hardwood forests |
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![PIF](Pif_sm.JPG) |
Swainson's Warbler
(29, AI=5, PT=3, TB=
4; % population - 20.8) |
Occurs throughout in forests with significant shrub layer
(perhaps not in the wettest sites). |
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![PIF](Pif_sm.JPG) |
Swallow-tailed Kite
(28, AI=4, PT=3, TB=
4; % population - 25.1) |
Presumably occurred throughout until largely extirpated in the
20th Century. Now definitely known to breed only in the Atchafalaya system in
Louisiana. |
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![PIF](Pif_sm.JPG) |
Cerulean Warbler
(28, AI=3, PT=4,
TB=5; % population - ) |
Only breeds in large, relatively dry forest blocks with tall
emergent trees from central Arkansas north. |
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![PIF](Pif_sm.JPG) |
Prothonotary Warbler
(24, AI=5, PT=2,
TB=4; % population - 34.8) |
Occurs throughout; uses wettest portions of forests. The area
needs of this and other priority forest birds are assumed to less than any of the three previously
listed species. |
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![PIF](Pif_sm.JPG) |
Northern Parula
(23, AI=5, PT=5,
TB=3; % population - 6.9) |
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Secondary growth |
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![PIF](Pif_sm.JPG) |
Painted Bunting
(24, AI=3, PT=5,
TB=4; % population - 4.4) |
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![PIF](Pif_sm.JPG) |
Bell's Vireo
(23, AI=2, PT=3,
TB=4; % population - 1.0) |
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Moist cleared land |
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![PIF](Pif_sm.JPG) |
shorebirds -
There may be more use of moist soil in the Mississippi Alluvial Valley
now during migration than years ago when the Valley was forested and better shorebird habitat
was more common to the west. |
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![PIF](Pif_sm.JPG) |
waterfowl -
This is a major wintering area for Mallards and other ducks as well as
excellent Wood Duck breeding habitat. These birds use both bottomland hardwood forest and
open wetland habitats. |
Notes: Pre-European percentages of population of priority birds was probably
very high considering that probably only 10% of the prior forest now serves as effective bird
habitat. This physiographic area presumably served as core habitat for the extinct Ivory-billed
Woodpecker and Bachman's Warbler. |
Complete
Physiographic Area Priority Scores (Zipped, Dbase5 file 288K)
Key to Abbreviations: AI-Area Importance, PT-Population Trend, TB-Threats to Breeding.
Priority Setting Process: General /
Detailed |
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Conservation issues and recommendations - The Mississippi Alluvial Valley
was entirely covered by bottomland hardwood forest at the time of European settlement, when it
was the largest extent of that habitat type on earth. Since then, over 80% of the forest has been
cleared for agriculture and other uses and the hydrology has been drastically altered, inhibiting
many aspects of ecosystem function. Much of the remaining forest remains in small fragments,
further reducing the capacity of the landscape to support bird populations. In recent years,
however, forest clearing has essentially stopped and restoration has probably increased total forest
coverage.
The area is mostly in private ownership, but there are numerous small to moderate-sized
federal and state wildlife reserves. Much private forest land is owned by the forest products
industry or limited partnership hunting clubs and is thus likely to remain forested. Well-drained
land is valuable for agriculture and most current forested lands or areas likely to be restored are
poorly-drained. This is the biological core of the Lower Mississippi Valley Joint Venture, and the
focus of a good deal of reforestation effort. Because the remaining forest is so fragmented,
conservation recommendations focus on retention or restoration of blocks of forest of sufficient
size to support healthy populations of the suite of bottomland hardwood forest birds. In southern
reaches, some of these should be 100,000 acres or more to support Swallow-tailed Kites and all
associated species. To the north, 20,000 acres including at least some drier habitat should be
sufficient for Cerulean Warblers and all other birds. Throughout, where blocks of that size are
unattainable, a 10,000 block will support Swainson's Warblers and all other less area-demanding
species. The total number of blocks to be retained or restored is about 70? and should include
about one million reforested acres.
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