Wetland Birds Demand Change

Though declining for years, some species may rebound in dynamically managed habitats.

by Nancy Shepherdson

Early each June for the last 14 years, natural heritage biologist Brad Semel has been throwing his hip waders in the back of his pickup and heading out before dawn to study nesting wetland birds. Sliding a canoe out into the dark waters, he searches for birds in one of 196 wetlands his team has studied all over the Chicago region.

In the last few years, he’s also taken along another vital bird-study tool: an MP3 player. It replaces a boom box that, he says, “had a bit of trouble coping with the water.” For shyer birds like the rails and bitterns, he’ll play their calls as he passes likely stands of cattails. If any respond, he’ll sneak into the cattails, looking for evidence that the elusive birds are nesting. He usually won’t see the birds themselves, he says, because they are “secretive, prefer dense vegetation, and slink around.” Often, though, he’ll find their nests, eggs, or young.

What Semel, who works for the Illinois Department of Natural Resources (IDNR), has discovered is bad news for wetland birds. Of 12 species analyzed for a forthcoming paper entitled “Long-term Declines of Wetland Dependent Birds in a Rapidly Developing Landscape,” ten have shown declines since the study began in 1980. The study found especially precipitous declines in populations of the common moorhen, American coot, black tern, blue-winged teal, sora, and yellow-headed blackbird. Only two species are actually thriving: the mute swan and sandhill crane. Mute swans show up, Semel found, when marshes have high water and few cattails. Sandhill cranes, on the other hand, like wetlands that are almost completely choked with plants, the better to hide their nests.

The study is the first to document, over such a long period, the significant decline of many wetland birds in the region.

But what Semel and co-authors Michael Ward and James Herkert also discovered is that, with adequate management, many of our local wetlands could support many more nesting wetland birds. By reviewing other studies, the researchers ruled out the birds’ reproductive health as a cause for the declines, and so began looking at habitat.

“What most birds like is an intermediate range of wetland called a hemi-marsh,” says Herkert, Peoria-based director of science for The Nature Conservancy of Illinois, who helped analyze data gathered in the Northern Illinois Wetland Bird Survey (NEWS) from 1980 to 2005. “At one extreme is an open-water wetland; at the other is closed wetland, completely covered with cattails. Most wetland birds like a mixture of 50 percent open marsh and 50 percent vegetation that occurs when wetlands are allowed to flood and dry.”

These days, this natural cycle of flooding and drying results in a hemi-marsh in only a handful of regional wetlands. These few exist because they are still adequately buffered by absorbent open lands and watersheds unaffected by highly altered landscapes of development. But such a natural situation is relatively rare, and becoming rarer.

Urban Wetlands

In urban areas, the study showed, the tendency is for wetlands to move to one of the two extreme conditions (an open pond or closed cattail marsh) and remain that way. Development “hardens” the landscape with buildings, pavement, and artificial drainage, altering natural water flows. Using aerial photos, the study correlated a pronounced loss of hemi-marsh with large increases in real estate development within two kilometers of the wetlands. Because there is legislative protection against filling the wetlands themselves, Herkert says, “the problem is not necessarily the loss of wetland, but rather the loss of variability and the characteristic changes in hydrology” that produce healthy wetlands and support a wide range of bird species.

“The good news,” says Herkert, “is that it’s possible to build water control structures to mimic that dynamic, even if the wetland has been altered.”

The tall, slightly weathered Semel showed me the variety of water management structures at Moraine Hills State Park in McHenry. They have all the beauty of manhole covers and concrete bunkers. Simple structures such as wooden boards and valves in the structures allow site managers to control water levels with the precision of a few inches. And they are currently creating some of the region’s most “productive” wetlands, including Black Tern Marsh, part of Moraine Hills.

“Black Tern Marsh was a sod farm, preserved behind levees on the Fox River. When the state took over, a decision was made to put in water control structures to keep the water level high,” Semel told me. What happened to the birds would have been predictable had site managers had the current study in their hands. Black Tern Marsh ultimately became an open pond, habitat for mute swans and not much else.

“So one of the first things I did after taking this job was to pull the boards out of the water control structure on the Fox River, to dry it out and expose the mud flats. I must have heard from every birder in northern Illinois, many of whom said I was killing the marsh and everything in it. I really started second-guessing my decision. Then a lot of migratory birds came back the next season, followed by the wetland nesters as healthy marsh vegetation lying dormant in the seed bank sprouted. By the second growing season, we had an outstanding population of yellow-headed blackbirds, prothonotary warblers, common moorhens, and more. Seeing all of those species return,” he said with a smile, “was testimony to making the right management decision.”

Semel has been responsible for the NEWS database and the study since 1994, and says that the sites under study are continually being updated. “We may add sites when told about them or drop sites if we don’t find anything several years running.” Or, he adds, if he finds a Wal-Mart built on a wetland.

At the same time, the Chicago Wilderness wildlife task force, of which Semel and Ward are members, is trying to coordinate implementation of water control and wetland management on a “landscape scale.” In other words, ideally, if a wetland must be drained to promote emergent vegetation or given more water to clear out tight cattails, planners will ensure that there is a good hemi-marsh nearby to which the birds and other fauna may migrate.

“The wildlife task force started getting together about a year ago,” says Ward, a research scientist with the Illinois Natural History Survey. “Now that we have the study, we know how important it is to have a coordinated effort among our agencies — you don’t want to have them all down [drained] at the same time. Site managers are also time-stressed and we can help them decide which sites should be drained and how often.”

Members of the task force will also be doing their best, Ward says, to educate the public about what it means for the good of wildlife when wetlands turn into mud flats for a season. “Our study is intended to highlight that if something isn’t done, these species could be extirpated in Illinois.” But there is also reason to hope. “Change happens very fast in wetlands.”

The study is under review for the journal Biological Conservation. Know of a good wetland on private property that might be included? E-mail brad.semel@illinois.gov.

Related articles:

Saving Habitat for Birds, CW Spring 1998

Birds and the Habitat: What Works for the Local Avians, CW Spring 2000

Birds of the Shrublands, CW Fall 2005

Plight of the Common Bird, CW Fall 2007