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Hendrickson Marsh is wildlife oasis

HENDRICKSON MARSH is not a huge wetland complex, but it is just one of many wildlife havens each spring and fall during migration times. Wetlands from the prairies of Canada, the Dakotas, Minnesota, Iowa, Missouri, Arkansas and Louisiana function as a place for waterfowl, shorebirds and songbirds to refuel their bodies. Wetlands are similar to the buffet line at a well known caf or supper club, an all you can eat special just for the wildlife that need it the most.

Right now, water levels at Hendrickson Marsh are being drawn down on purpose. This shallow basin has a big watershed and is easily refilled, assuming normal rainfall events. That assumption can create a problem however beyond the wildlife bureau folks intentions. A year with lots of rain, or excess rain makes it hard to keep water levels in the marsh low enough for vegetative regrowth. The flip side of the rain coin is too little rain. So a draw down of water now is partly a roll of the dice in anticipation of fall rains returning. Those rains may or may not come about.

Still, the wildlife managers have to try their best to see if 2016’s weather events will allow for good wildlife food production. Only time will tell if the plan works. Judging by past decades of experience, the averages of weather guides all basic assumptions. And since every year is different, DNR folks can and must be flexible to adjust what they can do and leave the rest up to Mother Nature.

According to Josh Gansen, DNR Wildlife Management Biologist, Hendrickson’s management is complex. Why? Because the stop log structure is inadequate to allow for more precise water level control. The big watershed can easily gather rainfall runoff and refill the impoundment area before they are ready for it. New water at the wrong time kills vegetation before it can attain good height or seed. There is a large gate at Hendrickson’s dam that can rotate up, but it allows water to flow from the bottom only. This is not a good system for water level control. Recognizing these limitations, the staff is doing the best they can with what they have to work with. The best case scenario is to develop a plan, and funding, to modify or replace the water control options at the dam.

The land in and around what had been called Kimberly Marsh, later to be named Hendrickson Marsh, was purchased by the Iowa Conservation Commission during the mid 1960s. This wetland and associated uplands was officially named after an Iowa State University professor of wildlife, George Hendrickson at a dedication ceremony on June 13, 1970. The original purchase was for 601 acres. In 1988, an additional 178 acres was added. The final 35 acres was included in later years. Total land and water area is now 821 acres. The site is located in far southwest Marshall and southeast Story County. From Rhodes it is approximately two miles west on county road E-63.

This wetland got its start a long time ago. Its origin dates to the most recent of glacial ice systems, what geologists call the Wisconsinan time frame. That glacial system reached its maximum southern advances across the entire northern part of the United States roughly 20,000 to 15,000 years ago. But its beginning was likely hundreds of thousands of years prior to the return of warmer melting times. As always in glacial cycles, the earth warmed naturally. Glacial ice edges and margins grew thinner, weaker and melted. The retreat of glacial ice is not the backward movement of glacial ice hundreds of feet thick, but simply the response to warming and warmer times brought on by the power of the sun, earth’s orbital tilt and other huge factors of galactic origins. The spot we now call Hendrickson Marsh was along the east marginal edge of one ice flow segment.

As glacial ice melts, lots of debris imbedded in the ice falls out, and accumulates or is eroded out of the ice. Water volumes running away from glaciers was tremendous and powerful. Around the edges of one large ice mass, a block if ice became isolated somewhat from the main glacial mass further north and west. This large ‘ice block’ slowly and methodically released its hold of water and debris to form a basin-like area. The kind of debris encased in glacial ice includes rocks big and small, gravel, ground up organic material from far northern locations, and lots of finely ground up material that forms the basic ingredients of soil. The resulting land forms in or near present day Hendrickson Marsh reflect those glacial historical facts.

And if we go back in time to about 2.5 to 2.1 million years ago, Iowa geologist have found convincing evidence of at least eight past glacial episodes. This evidence is written in the rocks and bedrock topography of our state. Glaciers come and glaciers go, and have done so multiple times. Glaciers grow due to the earth getting colder, and given enough geologic time, melt as the earth naturally rewarms. In human terms, glaciers don’t do anything fast. What is known is that Iowa has been totally covered with glacial ice many times in the past for long periods of time, and followed by relatively shorter inter-glacial warm times. Then the whole process repeats itself. We currently live during an inter-glacial time frame and thrive because of our adaptability as humans. We make the land work for us in food production, industry, transportation, and places to live.

Interglacial warm periods allow new plant growth to take place on exposed glacial till soil parent material. First to set roots are tundra-like vegetation types. That in turn is slowly replaced by coniferous trees such as spruce, larch, hemlock, fir and yew. Vegetation zones follow the glacial ice margin’s retreat. As warming continues, deciduous trees dominated. Still warmer times allowed grasses to dominate the landscape, replacing many trees. Ancient animal life filled each of those ecosystems. Animal skeletal remains tell scientists that mastodon, mammoth, musk ox, bison, caribou, camel, giant sloth, giant beaver and dire wolves lived in those past times. Human occupation dates back to the Paleo-Indian interval of 9,500 to 7,500 years ago.

Fast forward to today, Hendrickson Marsh can be considered one chapter in a very large book about how our landscape has evolved over time, adjusted to icy glaciers, and readjusted to ice free conditions. As humans who how live on this land, understanding the geologic past is important to how we adapt to life and living. The next time you visit Hendrickson Marsh, remember this short narrative about how it came to be in the first place.

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IOWA RIVER water flow rates have increased a bit due to last weeks rain events. The river crested at about 14 feet on Thursday. To help put this 14-foot level into some category for comparison, its waters are now about 3 feet higher a “low” flow whereby lots of sandbars are exposed. In other words, a river stage of 11 feet is perfect for canoes or kayak travel. So at this time, and probably for another week barring no big new rains, the use of the river for boats with outboard motors is a doable outdoor excursion. Marshall County Conservation Board boat ramps are located at the Forest Reserve, Timmons Grove, Furrow Access and Three Bridges. Once the river flow drops to near 12 feet or lower, outboard engine watercraft will have a difficult time traversing its waters. From 12 to 10.5 feet is definitely canoe/kayak time.

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This weekend was the FREE FISHING WEEKEND as designated by the DNR. No license is required. Fish take limits do apply however. Since today is Sunday, the last of the three-day free fish time frame, take the kids or family to a pond, lake or river for quality time outdoors. Also, keep the date of June 18 from 8 a.m. until noon available. That is the time for a KIDS FISHING DERBY at Riverside Cemetery in Marshalltown. The Izaak Walton League is just one sponsor for this fun morning of fishing. Prizes will be awarded.

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This week will mark the start of WILD TURKEY hens hatching their eggs. Soon little turkey poults will be tagging along their mothers learning how to survive. Outdoor enthusiasts can assist DNR forest wildlife personnel with turkey counts. Especially during July and August, if hen turkeys are seen with their broods, mark the date and general location. Then e-mail the information to this address: www.surveygizmo.com/s3/2115256/Iowa-Wild-Turkey-Reports. An easier method may be to call Jim Coffey at 641-774-2958.

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The 2016 Spring Wild Turkey season ended on May 22. Now that time has allowed all reports to be submitted, it appears that Iowans took 12,173 Toms or bearded hens. Marshall County hunters reported killing 70 birds. he top 10 counties in the state illustrate habitat conditions and lots of forest areas. They are in descending order…Clayton 583, Allamakee 410, Warren 407, Jackson 359, Appanoose 328, Madison 290, Monroe 286, Decatur 284, Winneshiek 282, and Harrison with 281.

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Advice from a river: Go with the flow; Immerse yourself in nature; Slow down and meander; Go around obstacles; Be thoughtful of those downstream; Stay current; the beauty is in the journey!

Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at PO Box 96, Albion, IA 50005.

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