Upper Midwest Environmental Sciences Center

The Upper Mississippi River flows through the heart of the Driftless Area,a region that escaped glaciation during the most recent glacial advances.

Nesting studies are used to assess habitat quality.

Extending over portions of the states of Iowa, Minnesota, Wisconsin, and Illinois, the Driftless Area’s distinctive bluffs and valleys are remnants of the melting glaciers: dissected, upland plateaus with steep bedrock ridges descending to river drainages that ultimately flow to the Mississippi River.

Climate, soils, topography, fire, and herbivore grazing interacted in the post-glacial period (10,000 yr B.P.) to create a complex landscape mosaic comprised of various types of prairie, oak savanna, and oak woodland over a large area of the Midwestern United States. Midwestern savannas represented a transition zone between the eastern deciduous forest and the tallgrass prairie. Periodic climatic fluctuations favored either prairie (dry, warm periods) or woodlands (cool, wet periods). In Wisconsin alone, oak savannas, barrens, and open woodlands occupied about 11 million acres; today less than 500 acres (<0.01%) survive. In the Midwest as a whole, oak savannas occupy only 0.02% of their estimated presettlement area. Nearly all of the former oak savannas in the Driftless Area have succeeded to closed canopy oak forests under fire suppression or were converted to cropland.

These oak forests now support a diverse set of forest-nesting birds. There is considerable interest in managing these forests to support species of conservation concern. Land managers struggle to define restoration goals for these forests, given their historical condition and the practical limits of modern management. Problems include regenerating oak-dominated stands in the absence of fire and forest invasion by exotic shrub species. Most forest land is owned by small, private landowners; timber management practices vary greatly and are strongly influenced by economic forces (timber values).

Prothonotary warblers occupy large floodplain forests in the Midwestern U.S. Much of the Upper Mississippi River floodplain north of St. Louis is owned by the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers. Wide, diverse, floodplain forests are globally rare, have high bird species richness, and provide breeding habitat for landbird species of concern . Floodplain forests rival all other habitat types in bird species richness, and bird abundances in floodplain forests can be twice as high as upland forests. Even though wide floodplains support more species than narrow, even small patches of floodplain forest in large river systems can provide valuable habitat for forest-nesting songbirds.

We studied floodplain and upland forests from 1991-2001.

However, floodplain and riparian ecosystems are in trouble globally and regionally. The area of riparian forest in the North-central U.S. in 1940 was estimated at 6.9 million ha, dropping to 5 million ha in 1980 (-27.5%). Midwestern states have lost 20-90% of their presettlement riparian forests. Many rivers and streams have been altered by channelization, levees, and locks and dams; changes in hydrology are affecting riparian forest regeneration in the Upper Mississippi River. For example, tree species and age class diversity in floodplain forests of the Upper Mississippi River is lower than it was historically. Silvicultural efforts to regenerate and diversify these forests are hampered by a high water table and competition from invasive species. These long-term changes in floodplain forests have the potential to alter breeding habitat quality for some landbirds.

We studied the bird communities of floodplain and upland forests of the Upper Mississippi River basin from 1991-2001. We described the assemblages of birds found in upland vs. floodplain forests, studied their nesting ecology, and learned how these birds are affected by forest succession, flooding, cowbird parasitism, and forest fragmentation.

Project was completed in September 2001.

Research helps resource managers make sound decisions.

Principal Investigator: Melinda Knutson

For more information, see these publications:

• Fox, T. J., M. G. Knutson, and R. K. Hines. 2000. Mapping forest canopy gaps using air-photo interpretation and ground surveys. Wildlife Society Bulletin 28: 882-889.

• Gustafson, E. J., M. G. Knutson, G. J. Niemi, and M. A. Friberg. 2002. Evaluation of spatial models to predict vulnerability of forest birds to brood parasitism by cowbirds. Ecological Applications 12: 412-426.

• Knutson, M. G., G. Butcher, J. Fitzgerald, and J. Shieldcastle. 2001. Partners in Flight Bird Conservation Plan for The Upper Great Lakes Plain (Physiographic Area 16). Pages 51. U.S. Geological Survey Upper Midwest Environmental Sciences Center in cooperation with Partners in Flight, La Crosse, Wisconsin. http://www.blm.gov/wildlife/pifplans.htm.

• Knutson, M. G., S. J. Gutreuter, and E. E. Klaas. 2000. Patterns of artificial nest depredation in a large floodplain forest. Journal of Wildlife Management 64: 576-583.

• Knutson, M. G., R. K. Hines, C. M. Sveum, T. J. Fox, and C. E. Korschgen. 1999. Floodplain forest songbirds of the Upper Mississippi River. Passenger Pigeon 61: 307-310.

• Knutson, M. G., J. P. Hoover, and E. E. Klaas. 1996. The importance of floodplain forests in the conservation and management of neotropical migratory birds in the Midwest. Pages 168-188 in F. R. Thompson, ed. Management of midwestern landscapes for the conservation of neotropical migratory birds. General Technical Report NC-187. U.S. Forest Service, North Central Forest Experiment Station, St. Paul, Minnesota.

• Knutson, M. G., and E. E. Klaas. 1997. Declines in abundance and species richness of birds following a major flood on the Upper Mississippi River. Auk 114: 367-380.

• Knutson, M. G., and E. E. Klaas. 1998. Floodplain forest loss and changes in forest community composition and structure in the Upper Mississippi River: a wildlife habitat at risk. Natural Areas Journal 18: 138-150.

• Knutson, M. G., L. E. McColl, and S. A. Suarez. 2005. Breeding bird assemblages associated with stages of forest succession in large river floodplains. Natural Areas Journal 25: 55-70.

• Knutson, M. G., G. J. Niemi, W. E. Newton, and M. A. Friberg. 2004. Avian nest success in midwestern forests fragmented by agriculture. Condor 106: 116-130.