1.  Clean water is essential to support a diverse group of animals.  Although amphibians and insects are especially sensitive to water quality, all animals require a certain level of water quality.  The decline of amphibians and the disappearance of chorus frogs and spring peepers suggest that the water quality problems of the Class of 1918 Marsh may be causing declines in animal populations.

Leopard Frog. Amphibians are more sensitive to water quality than many other animals.

2.  Plants provide food and shelter to animals.  The lack of plant diversity at the Class of 1918 Marsh probably limits the animals that use the area.  Many marsh animals do not like the dense and uniform stands of hybrid cattails.  However, some marsh birds like dense cattails, such as Sora Rail, Marsh Wren, Common Yellowthroat, and Red-winged Blackbird, and nest successfully at the Marsh (Lenehan, 2002).  A diverse plant community produces a wide variety of food which becomes available at different times through the year.  When only a few plant species are present, only a few types of food are available and only during a portion of the year.

3.  Water level is a crucial determinant of the animals that will use a marsh.  Different species like different water levels.  Diving ducks like deep water.  Dabbling ducks, the usual type of duck in the Marsh, prefer shallow water so that they can reach the bottom without diving.  Shorebirds prefer mudflats.  Marsh birds like emergent vegetation including cattails.  In a natural marsh, water levels are highest in the spring when spring runoff raises the water levels.  Although water levels fluctuate with rainfall, the water levels tends to decline through the summer before rising some years with fall rains.  There are many components of water conditions including:

a.  The proportion of open water and emergent water (James Zimmerman recommended that half of the Marsh be open water and half of the Marsh be covered by emergent marsh vegetation like cattails (Zimmerman, 1972)).  This proportion was a theoretical optimum for waterfowl and marsh species.  Through its history, the proportion of emergent marsh plants (mostly cattails in recent years) has varied widely at the Marsh.  In the early periods the Marsh was very open because it was a cornfield.  It was also very open after the muskrat “eat out.”  Today the percentage of the Marsh covered by emergent vegetation is between 35 and 50%, close to the desired ratio.  However, due to its dense growing patterns, the hybrid cattail monoculture is an inferior habitat when compared to a mix of emergent water plants.

b.  The depth of the deepest area (James Zimmerman recommended that the deepest portion of the Marsh be 6 to 8 feet deep (Zimmerman, 1970)).  A deep center prevents the Marsh from freezing completely and allows fish, amphibians, and other animal species to overwinter in the Marsh.  Having these species live in the Marsh decreases mosquitoes and provides food to support a more diverse animal population. If the center of the Marsh was ever 6 feet deep, it is probably not now.  It appears that dabbling ducks can reach the bottom in almost all areas except when the water is at its highest level. 

c.   The steepness of the edges  (James Zimmerman recommended gradual sides where the depth changed about one inch per foot (Zimmerman, 1970)).  Gradual edges would encourage the use of the Marsh by shorebirds and wading birds.  Currently the steepness of the edge is hard to estimate because hybrid cattails cover the entire area.   However, in at least some areas the slope has become much steeper and there are deeper holes.

d.  The rate of change of water levels  Sudden changes in water levels can be disruptive to animals.  For instance, during the nesting season, going from very low to very high water levels can submerge bird nests. Rapidly rising water is a problem in the Class of 1918 Marsh because this 14-acre Marsh drains 125 acres of urban area.  Due to the high degree of impermeability in this urban area, a rapid rain can result in a large inflow of water.  This was the case in the flood year of 2000 when most birds were forced to nest a second and in some cases a third time.   Likewise, going from high water levels to low water levels can leave nest high and dry and vulnerable to predation.   In many cases this is preventable.  Usually this type of rapid and dramatic decline in water levels is caused by pumping water out of the Marsh up into the higher University Bay.  In 2000 after the rains stopped, the Marsh was rapidly drained to a low level that caused further nesting failures.

e.  The seasonal fluctuation of water levels As noted above, in most Wisconsin wetlands levels start high and generally go down through the season.  In recent years the level of the Class of 1918 Marsh has been drawn down in early spring so that extra runoff can be caught by the Marsh and then the water levels have been allowed to rise into June.  As a result, birds are forced to nest a second time because their nests are flooded.  The reason for this type of management is that the Class of 1918 Marsh is a retention pond used to control water  levels.  Furthermore, due to the low level and crucial equipment in the Nielsen Tennis Stadium basement, the Marsh level cannot be allowed to go above a certain level without flooding crucial University equipment.  Low water levels in the late summer and fall promote shorebird usage.  However, low levels in the early and mid summer can cause nesting failures because nests are vulnerable to predation and when the Marsh dries up there is not enough food for Marsh bird young.  In 2001 the Marsh dried up early, dramatically decreasing the reproduction in the Marsh.  Low summer water levels may prevent submergent vegetation from growing and limit the food for fall ducks (Vander Zouwen, 1983).

4.  The size of the habitat and adjoining buffer areas affects the reproductive success of Marsh animals.  Recent US Fish and Wildlife recommendations suggest having five times as much upland as lowland habitat for waterfowl nesting.  Currently, there are about 14 acres of Marsh and about 1 acre of upland habitat inside the path, far less than a one to one ratio.  Furthermore, the upland habitat inside the path is mowed periodically and in other ways disturbed, making it less than a full acre of usable habitat.

5.  The amount of disturbance and number and type of predators affects animal breeding success.  The Class of 1918 Marsh is a highly disturbed area.  In addition to walkers and joggers, bikers, lawn mowers, and frequently trucks drive around the edge.  People bring their dogs and let them run through the limited edge habitat.  The Marsh is hunted by a variety of predators ranging from Raccoon to Coopers Hawk, Mink and Coyote.  Due to the limited amount of buffer habitat, marsh animals are vulnerable to this hunting pressure.

Possible Solutions:

1.  Improve water quality.  For more information on improving water quality, follow this link:

2   Increase plant diversity.  For more information on increasing plant diversity, follow this link:

• Dominant Plant Species and Possible Solutions

3.  Water levels at the Class of 1918 Marsh are a very complicated issue.  In general, to the extent possible, manage the Class of 1918 Marsh water levels for wildlife rather than for flood control and water retention.   Possible solutions to these challenges are discussed below.

a.  Although the ratio of emergent vegetation to open water appears to be appropriate, the hybrid cattails that compose most of the emergent vegetation need to be managed in order to encourage a more diverse community of marsh plants.    

b.  Measure the water depth of the deepest areas.  If this depth is less than six feet, consider dredging or digging out a small area in the center to provide refuge for aquatic animals to overwinter.

c.  As the cattails are opened up, consider grading the banks to make them gradual.

d.  Manage water levels as much as possible to mimic natural flows.  Try to have the highest water levels in April rather than June.

e.  Unless flood conditions exist, draw down the water levels gradually rather than suddenly.  If necessary, bring in water from University Bay to maintain early summer water levels for nesting birds or to attract migrant waterfowl in the fall.

4.  To the extent possible, manage the vegetation of the Marsh and its edges for wildlife.  Increase the amount of habitat.  Eliminate mowing inside the path during the spring and summer unless it is required as part of a well considered, systematic attempt to eliminate non-native invasive species.  Where possible, increase buffer zones by planting native plants on the outside of the path.  In other areas, leave the grass longer at the edge of the playing fields nearest the Marsh. 

5.  In order to decrease predation, increase buffer zones (see 4).  Prohibit dogs (and cats) from April through July.  Fine people with dogs off leash during this period.  Discourage disturbance including motorized vehicles on or inside the Marsh path.  Consider live trapping and relocating excessively abundant predators like Raccoons.

Sources:

Lenehan, R.  2002.  Campus Natural Areas Breeding Birds 2000, 2001, 2002.

Vander Zouwen, W.  1983.  Waterfowl Use and Habitat Changes of a Refuge in Southern Wisconsin:  1947 – 1980 and Vegetation Change in University Bay from 1966 –1980.  University of Wisconsin – Madison.  MS thesis.

Zimmerman J.  1970.  Memo on University Bay:  University Bay Natural Area Management – specifically the former cornfield.

Zimmerman, J.  1972.  Class of 1918 Marsh Signs.  University of Wisconsin Arboretum.  University of Wisconsin  Foundation.

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