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Tomahawk Marsh is returning to its prairie and wetland heritage

  • 10/18/2022 1:01:00 PM
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Tomahawk Marsh is undergoing a facelift of sorts. Parts of the 428-acre wildlife area just north of Lake View in central Sac County, has been reshaped to create small seasonal wetlands, and many of the trees have been removed to reclaim the prairie and to emphasize the grassland and wetland ecosystem.

“We’re working to turn the clock back 100 years, before the tree encroachment started, and expand the usable space for grassland bird species,” said Keith Ringler, wildlife technician with the Iowa Department of Natural Resources’ Black Hawk Unit. “It will look different this spring when the trees are gone.”

Ringler said the plan is to remove trees from the portions of the area that will be seeded to prairie and staff will increase the frequency of prescribed fire to maintain the prairie, if Mother Nature cooperates.

Given its location adjacent to the county road and its neighbors, fire can only be used when the wind direction is out of the southwest.

The prairie conversion is occurring on different sections at different intervals. One field is working its way through the first year as a prairie where an adjacent field is in its fourth. The four-year-old prairie is filled with bugs for hungry grassland birds. The southern portion has newer reconstructed prairie featuring up to 120 different plant species, including side oats gramma, little bluestem, ironweed, compass plant, cup plant, and rattlesnake master.

The existing 70 acres currently in agriculture will continue to shrink as the conversion process continues. Some of that cropland is being farmed as part of the process to eliminate the seed bank from the hay field as it transitions from old hay to prairie.

The DNR is working with a local partner as part of the beginning farmers program to do the mowing required for a new prairie, the planting and spraying of the sunflower fields, and planting the food plots.

The goal of the management plan is to keep the native shrubs - ninebark, dogwood and plums - and to maintain about 35 acres in ag fields as small food plots of corn, soybeans, sunflowers.

Tomahawk Marsh’s main 167-acre wetland, ringed with cattails and bulrushes, is visible looking east off Perkins Avenue. It’s a good place to kayak during years with normal rainfall and watch birds during the spring and fall migration.  

Ringler said low spots hidden in the terrain were identified using new technology that allowed them to restore these smaller wetland pockets. These are often seasonally dry, but usually hold water in the spring. Tomahawk Marsh is in the Raccoon River watershed and the series of connected wetlands outlets to the southeast eventually entering the North Raccoon River.

The main marsh has hosted a pair of nesting trumpeter swans for the past 10-15 years, and had one breeding pair this year that produced five cygnets. It also has a history of Blandings turtles, snapping turtles and bullfrogs. There is remnant prairie along the marsh edge.

The Multiple Species Inventory and Monitoring team within the Wildlife Diversity Program visited Tomahawk Marsh in 2009 to survey the wildlife population and in addition to Blandings turtles and trumpeter swans, a number of species listed as in greatest conservation need were confirmed there, including northern prairie skink, northern leopard frog, American kestrel, chimney swift, common nighthawk, eyed brown (butterfly), and sedge sprite (damselfly).

Tomahawk Marsh also provides hunting for pheasants and waterfowl and recommended to callers who inquire about places to pheasant hunt in the vicinity of Sac County. Nontoxic shot is required on the area.

Looking at it from above, the area resembles a tomahawk, which is the source of its name.

Also visible from above is the old Chicago Northwestern railroad line that ran from Wall Lake to Sac City, from 1877-1972 as part of the line transporting coal from Wyoming to the Great Lakes. The railroad was the likely seed source for the trees the Black Hawk staff are currently removing. It’s also a good place to take a hike.

Staff are also working to control smooth brome and reed canary grass through late spring or fall prescribed fire. Fire is also a key technique in the battle against sericea lespedeza. Ringler said they’ve used fire for five years in a row on a 10-acre block of prairie, followed by spraying to expose the seed source and now, the once visible invasive is hard to find.