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Its size, habitat diversity and location make Sweet Marsh a top birding and duck hunting spot in Iowa

  • 9/18/2018 4:14:00 PM
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Tripoli, Iowa - Wildlife biologist Jason Auel received a rather unusual complaint from a resident near the Sweet Marsh Wildlife Area in northeast Bremer County.

The caller said a sandhill crane was attacking its reflection in their window, pecking the glass and window sills and they wanted some help. It wasn’t the first complaint he received about sandhill cranes – one earlier reported cranes eating a dozen acres of their corn.

“It had to be the first depredation call for damage caused by sandhill cranes,” Auel said.

Sandhill cranes have used Sweet Marsh as a stopping point during their annual migrations, some staying behind to become residents. This year, at least eight young were successfully hatched. The scratchy call can be heard from the south end of the marsh. In the spring, their numbers can reach 100 or more.

The spring migration is huge at Sweet Marsh with bird species numbering in the hundreds and bird watchers in the thousands. It was included as part of the Wapsi River Bird Conservation Area that was formally dedicated in 2007.

“It’s part of the Wapsipinicon River corridor which is an important migration highway. It’s common to get dozens of warblers, neotropical species, shorebirds and thousands of ducks and geese,” he said.

The spring migration is when Darrin Siefken begins his weekly visit to the marsh.

Siefken, of Tripoli, owns CrawDaddy Outdoors in Waverly that caters to people who enjoy the outdoors, which makes sense given his background as a Bremer County naturalist for 11 years. Siefken offers guided floats at Sweet Marsh Tuesday evenings from mid-March to mid-May.

During the two hour marsh tour, he points out different bird species, shows paddlers how the marsh is managed, and, with the help fellow Tripolian, Kip Ladage, offers photography tips.

“It’s an amazing area,” Siefken said.

For those not wanting to leave terra firma, there is a viewing area with a spotting scope overlooking the refuge on the southwest part of the marsh.


The Refuge

A roughly 200-acre waterfowl refuge in the southwest part of Sweet Marsh is closed to all access from Sept. 1 through the end of the duck season to allow waterfowl a place to rest and refuel on their journey south. It also provides shelter from bad weather and predators. This area is managed to provide millet, corn, occasionally soybeans or left idle to come up with annual weeds as food source to keep ducks around longer.

Duck hunting

Sweet Marsh Wildlife Area was developed in the 1950s as a stopover for ducks and has been popular with duck hunters ever since. Most of the hunters come from Bremer County and nearby Waterloo and Cedar Falls. 

It covers more than 3,100 acres, with eight miles of dikes, six parking lots and three boat ramps. It has five pools connected through a series of canals totaling about 800 acres of water that includes Martens Lake, the second largest impoundment in northeast Iowa. The largest boat ramp is on Martens Lake and it will fill with boat trailers on opening morning of duck season.

Water levels are manipulated during the year to provide seed producing annual vegetation ducks can use for food and to create tall vegetation where boat hunters can hide.

One reason Sweet Marsh is so popular is that its habitat diversity can support walk in hunters, kayakers and large boat hunters. For less competition, Auel suggests hunters consider going out during the week, rather than on the weekend.



About 16 years ago, a neighbor reported finding a massasauga rattlesnake in his garden. The snake was caught, outfitted with a telemetry device and released in the marsh to track its movements. What they learned was it overwintered in crayfish burrows. The snake disappeared.

The last encounter of a massasauga at Sweet Marsh was a dead one on the road by the Martens Lake parking lot in 2011. It hasn’t been seen here since.

Because of the potential for having a resident population of massasauga, Auel is required to follow federal guidelines to manage for this threatened species, like not mowing the dikes less than eight inches.

The massasauga is often mistaken for northern water snake that is also at Sweet Marsh. How to tell the difference

  • Northern water snakes are found mainly in and around water
  • Massasaugas tend stick to the prairie until hibernation
  • Northern water snakes are aggressive
  • Massasaugas are not aggressive
  • Northern water snakes feed on fish and frogs
  • Massasaugas feed on rodents, small mammals and frogs


Wild marsh life

Sweet Marsh is home to more than birds and fowl.

A black bear stayed here a few years ago and was seen swimming in Martens Lake. A moose and wolf have also wandered through.

The marsh is home to Blanding’s turtles - with confirmed reproduction - and central newts. Red squirrels are here too and they are protected. Its home to red shouldered hawks and has at least five bald eagle nests. Ospreys stop by for a fish meal on the way south for the winter. Sweet Marsh was one of the first locations where otters were reintroduced in Iowa.

Pale green orchid is found here – it’s not a showy flower, but it is rare. 

“It’s unique in size and habitat diversity that benefits from its location along the Wapsipinicon River corridor,” Auel said.


Other visitors

Students from Wartburg College, Upper Iowa University and Hawkeye Community College visit Sweet Marsh for class. A boy scout built and installed an osprey nesting platform for his Eagle Scout project.

Mowed dikes are used for their easy access by kayakers, hikers, deer hunters and duck hunters with their bags of decoys.


Wild edibles

Sweet Marsh is a hotspot for wild asparagus, strawberries and mushrooms. Mushroom hunters stop at different times of year to search for morels, oysters, puffballs and chicken of the woods. Puffballs here have been the size of a volleyball.