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Published on: 4/11/2007
Last Visited: 5/14/2007
"We are attempting to restore our native grassland," said Refuge Manager Dan Severson."It's not the tallgrass prairie.That was farther east.And it's not the shortgrass prairie like in Montana.It's a low, sparse midgrass prairie, with needlegrass and western wheatgrass as the vegetation type."
The prairie restoration effort is relatively new in the history of Des Lacs NWR, which was established nearly 70 years ago."At one time, we managed the refuge for the production of mallards," Severson explained.
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"We can manage that for the most populous and popular species, like mallards and whitetails," said Severson."I'm a hunter myself, and I understand the people's interest in that.But the Service feels we need to manage for native grasslands."
The idea is to restore continuous tracts of native prairie to benefit the migratory bird species whose populations are in the most trouble and which rely specifically on grassland habitat."They like shorter, sparser cover than what we have," Severson said.
In particular, he mentioned the Baird's sparrow, pintail ducks, Sprague's pipit and chestnut-collared longspur as species dependent on midgrass prairie.Numbers of pintails have been declining in recent years, and the USFWS has identified the Baird's sparrow, Sprague's pipit and longspur as "Birds of Conservation Concern" in the United States.
Those birds, along with others like LeConte's, grasshopper, clay-colored and savannah sparrows, burrowing and short-eared owls, and upland sandpipers, will nest successfully only in the sparse vegetation typical of the midgrass prairie.
"We're managing for endemic species that rely on grassland," said Severson, "and they can't change."
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"The units in the best condition now are the largest areas of the refuge," Severson said.
Those units are primarily located at the northern end of the refuge, with more than 7500 upland acres.Severson described that area as having fewer trees, or less "edge," the term used to describe features like tree groves, fence lines or roads that disturb the open character of grasslands.
Stands of trees on the refuge create habitat for predators like skunks, raccoons, deer mice and several species of hawk that wouldn't normally thrive on open prairie.However, a bit of woodland habitat allows them to prey successfully on grassland birds and their nests."In a ten-yard tree row, edge effect can be up to a hundred yards out," Severson said.
The presence of some raptors, such as falcons that feed on other birds and owls, often discourages endemic raptors like the northern harrier and the ferruginous hawk from using a grassland area."There are no ferruginous hawks nesting on the refuge now," Severson said."They are the true prairie nesting hawk."
Brood parasitism, where one type of bird unknowingly hatches the egg of another, also becomes a problem with edge effect."Brown-headed cowbirds, a common woody edge species, will perch and watch [grassland] birds nest," Severson explained, adding that cowbirds then move in and lay their own eggs, which causes the true parents to abandon the nest or raise a cowbird chick instead of their own.
The undesired vegetation in a unit dictates the strategy used by refuge staff."In the units dominated by brush, some need fire," Severson said."In the brome-dominated units, we've reduced the density somewhat by fire.Fire won't take out smooth brome, but grazing will."
Refuge personnel combine the tools of fire and grazing."This year, 4500 acres will be grazed," said Severson.
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"We are using repeated prescribed fire to get rid of the brush," Severson said.
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"In private pastures, that gets grazed out," Severson said.
The third tool in the refuge's arsenal is relatively new."For the first time, we used a bulldozer on the north end," Severson said."Our goal was to knock down dead aspen groves that have been repeatedly burned."
The refuge staff has also worked at removing caragana from an old homestead site in the same area.According to Severson, fire was not effective in killing the caragana, which is another introduced species, so the bulldozers will clear the stand."Yes, it's deer habitat," said Severson, "but it's an invasive species and will spread."
The restoration efforts at the north end of the refuge have been intensive, but Severson maintained not all units of the refuge would be managed the same way."Other areas are so narrow that even if they were good quality, they wouldn't provide a lot," he said as he pointed on a refuge map to thin strips of land along the lake shores.
In fact, much of the rest of the refuge will stay as it is."We will continue to take out invasive caragana and Russian olive as possible on the north end," Severson said.
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Severson started working at the Des Lacs NWR in 1992 and conducted his first prescribed burn in 1993.Since then, results of the restoration plans have been mixed.Refuge personnel complete vegetation surveys on each unit of the refuge about once every 10 years."Vegetation changes slowly," Severson said, "but we can see change."
The frequency of brush and trees on the refuge's north end has been reduced, but smooth brome has increased in some of the units that have been repeatedly burned."They were units we couldn't graze," said Severson."We had to get rid of the brush first."
Bird counts have been taken following the restoration efforts, with increases seen in numbers of upland sandpipers and grasshopper sparrows.A few Baird's sparrows have now been observed nesting on the Des Lacs refuge.
Severson explained that once the western snowberry and silverberry in a unit could be knocked back with fire, the plan would be to graze that unit for three or four years, rest it a year, burn it and then graze it again to control the nonnative grasses and allow the native grasses like little bluestem, side oats grama and blue grama to reestablish themselves.
"As we get it in better shape, it will see more rest," he said."That helps native grasses, too."
Ideally, a healthy unit can be grazed for three or four years, rested one or two years, then burned one year before repeating the cycle."Studies have shown the fire return interval here was historically in the five to six year range," Severson said."But we're not there on any of [the units] yet."
He admitted that returning the vegetation to midgrass habitat would be difficult."I don't know if we can ever restore native prairie, but we can get different plants growing out there and use more management to fight smooth brome," he said.
Some area residents don't agreewith Refuge managementSeverson also understands some area residents may not agree with the removal of trees or prescribed burns, and that some hunters have complained about the loss of whitetail deer habitat.
"It's our duty to manage for the species in the most trouble," said Severson."We're not trying to duplicate the habitat that's most plentiful outside the refuge."
He continued, "The refuge's priorities are different than most hunters.
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"Even though those are popular gamebirds, that is not our mission," Severson said.
Since Severson's arrival, the Des Lacs refuge has made more hunting opportunities available for pheasants, deer and turkeys, and opened more retrieval roads during the deer rifle season.However, hunting use cannot overrule other refuge goals, especially those related to restoring native grasslands.
"I hunt, too, but we can't manage the place as a hunting reserve," said Severson."That's not our mission.
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