Study plots at the Neal Smith National Wildlife Refuge have shown that strips of native prairie embedded within monoculture farm fields can support Dickcissels and other grassland birds. Photo: Matt Stephenson

Conservation

On Midwest Farms, ‘Prairie Strips’ Give Grassland Birds Something to Sing About

Vibrant bands of native vegetation planted among crops can boost dwindling bird numbers while slashing nutrient pollution, researchers find.

In the 1830s, when homesteaders and their oxen began the brutal labor of plowing up deep-rooted native grasses to make room for crops, tallgrass prairie covered some 85 percent of Iowa. By 1881, when Tim Smith’s great-granduncle bought the Wright County land Smith still farms today, most of it was gone. Today, less than one-tenth of 1 percent of Iowa’s prairie remains. 

But in one corner of Smith’s 800-acre corn and soybean farm, the prairie is staging a modest comeback. Woven into one of his fields are two vibrant ribbons of native plants, averaging about 60 feet wide and together totaling three acres. “The prairie strips are a sharp contrast to the surrounding monoculture of corn and soybean fields,” Smith says. “It’s an amazing menagerie.” Big bluestem, sideoats grama, and other grasses wave in breezes bearing the bouquet of wild bergamot, butterfly milkweed, partridge pea, and more than a dozen other flowering plants. Dickcissels, Eastern Meadowlarks, and other native birds sing from wildflower perches, while Ring-necked Pheasants scoot through the understory.

Smith’s is among at least 55 farms in Iowa and six other Midwestern states with prairie strips, an agricultural conservation tool created in 2007 by a team of researchers at Iowa State University. Planted perpendicular to a field’s slope—either among the crops or on the field’s edge—the strips capture and filter rain-driven runoff before it reaches Mississippi River tributaries.  

These slices of habitat are mere glimmers of the vast, landscape-scale prairie restoration required to recover plunging populations of birds, pollinators, and other grassland wildlife. But such wholesale rewilding is a tough sell in the super-productive agricultural heartland. Prairie strips offer a middle ground, the researchers say—a way to soften some of commodity farming’s biggest environmental impacts while boosting biodiversity and creating habitat for species in desperate need of a toehold.

“Most farmers I interact with have a very strong conservation ethic, and struggle with how to keep soil and nutrients in place while also maintaining financial viability,” says Lisa Schulte Moore, co-leader of the Iowa State research team. “We have three farms that are adding more strips this year after having implemented their first strip two to three years ago. It’s exciting that they like the benefit-to-cost ratio and are feeling confident in their implementation.”

In 2017, Schulte Moore and colleagues published results from 10 years of research in the Proceedings of the National Academy of Sciences. Covering 10 percent of a corn or soybean field in native prairie strips yielded far more than a 10-percent improvement in environmental performance, they found. Compared to conventional fields, the strips slashed soil loss by 95 percent and cut surface runoff of phosphorus and nitrogen by 77 percent and 70 percent, respectively. Those findings raised eyebrows in a state where gully-carving rains wash away millions of tons of topsoil each year and water pollution from farm nutrients fuels litigation, requires costly water-treatment upgrades, and contributes to a Connecticut-size “dead zone” in the Gulf of Mexico. 

The benefits go beyond soil conservation and water quality, the paper showed. Researchers also found more than three times as many pollinating insects on fields with strips versus those without, and more than twice as many birds from species that Iowa considers to be of greatest conservation need. Now that the research has moved beyond study plots at Iowa’s Neal Smith National Wildlife Refuge and onto working farms, some members of the team are trying to better understand how birds use prairie strips and what role they can play in slowing the decline of species in peril.

For the past four years, Jordan Giese, a Ph.D. student in avian ecology at Iowa State, has led a survey of birds on 12 farms with prairie strips, including Smith’s. The study is ongoing, but preliminary results indicate that birds are 71 percent more abundant in fields with strips than in conventional fields, including those with other conservation measures such as grass buffer strips that provide less diverse vegetation. The team has counted more than three times as many Dickcissels, and more than twice as many Grasshopper Sparrows, Common Yellowthroats, and Red-winged Blackbirds in fields with strips. Dickcissel and Grasshopper Sparrow are both species of greatest conservation need in Iowa, and populations of all four species have declined sharply in the past four decades.

The narrowness of prairie strips leaves them unsuitable for species that need large, unbroken chunks of habitat, such as Bobolink and Northern Bobwhite, Giese notes. “But if we’re putting more birds on the landscape and some of those birds are imperiled grassland species, that’s good enough for me,” he says.

While Giese counts the birds using prairie strips, fellow Ph.D. student Matt Stephenson is focused on those building nests there. With their long edges exposed to the dangers of the outside world, strips may not offer nesting birds the same protection from predators and nest-parasitizing Brown-headed Cowbirds as being nestled deep in a large swath of prairie. “But all habitat on farms is already really narrow and linear and fragmented,” Stephenson says. “That’s Iowa—the entire state looks like that.” And compared to other linear habitat like grassy buffers, the thick, diverse vegetation in prairie strips seems to offer relative safety for nesting birds, his unpublished data show.  

In four field seasons, Stephenson’s team has found 1,261 bird nests from more than two dozen species on participating farms, and tracked them to see how many escape predators or other threats long enough for at least one chick to fledge. Nearly half the nests have belonged to Red-winged Blackbirds, a generalist species that can thrive in a wide range of habitat. But for other species, being tucked away among the dense, stiff-stemmed plants of prairie strips appears to make a big difference in nesting success. Vesper Sparrows—not a species on Iowa’s conservation concern list but one whose population has declined by 30 percent since 1970—fledge chicks more than five times as often in prairie strips than in other farm habitats, preliminary data indicate. Dickcissel nests fledged young more than twice as often.

In the next few years, Stephenson aims to publish a full analysis of nest survival rates for six to eight bird species in prairie strips and other kinds of farm habitat, and Giese hopes to document how bird communities change as prairie strips mature in the first few years after planting. “If we can get at what the mechanisms are for why birds do better in one place than in another, then we can start to design these conservation measures with birds in mind,” Stephenson says.

Meanwhile, the word about prairie strips is spreading among Midwestern farmers. When the annual Iowa Farm and Rural Life Poll publishes in the coming months, it will show that 56 percent of Iowa farmers surveyed had heard about the practice, and the majority of those polled said yes (15 percent) or maybe (39 percent) when asked if they’d be interested in planting strips, according to poll director J. Gordon Arbuckle. “I was amazed at how many farmers had heard about the practice, given that it’s only been a couple of years since the first ones were established on working farms,” he says.

Smith, 64, who has earned recognition for his conservation efforts, says his strips are earning their keep. To help offset his costs, he enrolled the strips in the federal Conservation Reserve Program, which pays farmers to plant habitat instead of crops. But he says he’d stick with them even without that incentive. “It makes it a little more difficult to farm, but it does protect the soil and prevent nutrient loss, and the wildlife benefits are there,” he says. “Once I got them established in the first couple of years, they pretty well take care of themselves.”

As word spreads through country cafés and co-ops, Smith expects more farmers will choose to brighten their fields with wildflowers and birdsong. “It’s got a ways to go,” he says, “but it has huge potential to benefit wildlife.”

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