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Dissected Till Plains
(Area - 22,394,200 ha)
Executive Summary |
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Location and physiography - The Dissected Till Plains occupy
much of Iowa, eastern Nebraska, northwest Missouri, and small parts of northwest Illinois,
southern Minnesota, and northeast Kansas. This area was glaciated, uplifted, and subsequently
eroded into a flat-to-rolling terrain that slopes gently toward the Missouri and Mississippi River
Valleys. Natural vegetation is a mosaic of tallgrass bluestem prairie and oak-hickory forest with
oak savannahs characteristic of transition zones. Bottomland hardwoods grow in river
valleys.
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Priority
Bird Populations and Habitats
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Grasslands |
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![PIF](Pif_sm.JPG) |
Greater
Prairie-Chicken
(27, AI=2, PT=3,
TB=4; % population - <1) |
This bird requires a large heterogeneous area of grassland; its
area demands exceed those of other grassland birds in this area.
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![PIF](Pif_sm.JPG) |
Henslow's Sparrow
(26, AI=2, PT=3,
TB=4; % population - 4.0) |
Breeds in late successional grassland (about 3-8 years post-
disturbance) with standing dead vegetation and a well-developed litter layer.
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![PIF](Pif_sm.JPG) |
Bobolink
(24, AI=3, PT=5,
TB=4; % population - 3.6) |
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![PIF](Pif_sm.JPG) |
Field Sparrow
(24, AI=4, PT=5,
TB=4; % population - 4.7) |
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![PIF](Pif_sm.JPG) |
Loggerhead Shrike
(24, AI=3, PT=5,
TB=4; % population - 2.4) |
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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 - This former upland
prairie/savannah/forest complex is now one of the most heavily altered physiographic areas in the
country. Agriculture dominates the uplands, fire suppression and urbanization encourage trees
where there was once prairie, and reservoirs have flooded many of the more extensively wooded
bottomlands.
About half of the agricultural lands are hay field or pasture which offer some potential for
use by priority grassland birds. Dominance of fescue and early mowing for hay, however, greatly
reduces much of the area's value. Protection or restoration of a series of grassland Bird
Conservation Areas each consisting of a 2000-acre core surrounded by a mile-wide matrix
containing at least 2000 additional acres of grassland may be the best hope for perpetuation of the
grassland species suite. Where prairie-chickens are not an issue, such a large central core may not
be necessary as long as patch sizes exceed minimum area requirements of other priority birds and
the percentage of grassland in the Bird Conservation Area remains 40% or greater. Smaller
grasslands specially managed or enrolled under the Conservation Reserve Program may support
one or a few priority species, especially if they help bring the total amount of grassland in a
landscape above some critical threshold. Restoration of riverine corridors offers promise for
forest birds if patches are large enough that predation and parasitism rates are minimized. PIF
suggests management of small upland woodlots for in-transit migrants.
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