Least bittern babies depend on their parents for a diet of fish and frogs. But they depend on us to save them some marshes.

by Sheryl De Vore

bobolink travels thousands of miles from its winter home in Argentina to find a place to raise its young. In early May, after long nights of migrating and stopping to refuel, it finally descends at sunrise upon its last destination: a grassland in Chicago Wilderness. At first, the black-and-white songbird with a cream-colored nape hovers and sings its delightful rollicking song, as it did here last year.

But something is wrong. Where large expanses of short grasses once grew, shrubs are now taking over. Red-winged blackbirds sing their onkalees, content with these shrubs as nest places. But the bobolink does not feel at home. It needs a different kind of habitat in which to build its nest.

A century ago, the bobolink's ancestors would have flown to other grasslands, where the shrubs had burned from natural fires. But today because of the immense loss of grasslands, that might not be possible. Instead, the bobolink will have to decide, after its long journey, whether it should remain here in summer and not breed, or expend more energy flying farther north where it may or may not find territory unclaimed by other bobolinks.

This story describes the plight of the region's rarest breeding birds, those of grasslands, wetlands, and savannas, and what professional and citizen scientists have been learning about birds and their survival gear here.

"When you talk about the conservation of birds, the rules are different for each suite of birds," says Dr. Jeff Brawn, an ornithologist with the Illinois Natural History Survey. Brawn and other scientists have been studying the abundance and breeding success for many of the rare birds of Chicago Wilderness. They are also being joined by citizen scientists, who help gather the information crucial for habitat stewardship.

Together they are learning that ecosystems consist of matrixes in which one bird species may need a larger territory, another may need a smaller one; one may be dependent on a certain water depth, and another may need a certain grass height, while another prefers breeding in a grassland that was burned three years ago. If there is no alternative, birds will often nest in marginal habitat, but they will be less successful in rearing young. The key to keeping a bird's population viable is for the bird to produce enough young to compensate for adult mortality.

As birder and citizen scientist Joe Suchecki said, "We're learning to maintain good habitat for birds, but we have so much more to learn. We have a lot of work to do before we know what it takes to assure a bird's survival." That's where the researchers come in — each of them studying the habitat requirements of birds as well as how well they succeed in reproducing young.

To discover the habitat needs of grassland birds, Jim Herkert of the Illinois Natural History Survey has been conducting a study of bird populations and nesting success at Midewin National Tallgrass Prairie in Will County and the nearby Goose Lake Prairie since 1995. The Midewin area contains thousands of acres of prairie and pasture, the largest assemblage of grassland habitat in Chicago Wilderness.

This year, with scores of volunteer birders providing additional data, he'll expand that study dramatically (see Bird Monitoring Pays Off). Herkert and his team have already learned that our different grassland bird species need different habitats, and that means very different challenges for managers. "If we managed a given prairie to be the very best habitat for bobolinks," Herkert explains, "we'd lose the Henslow's sparrows. If we managed just for the Henslow's, the bobolinks and grasshopper sparrows could plummet."

One of his latest discoveries is that bobolinks — one of the nation's fastestdeclining songbirds — and grasshopper sparrows are most abundant immediately after a fire. Their populations drop every year after that, until another burn occurs. Conversely, a burn eliminates habitat for Henslow's sparrows at first, he says, "but then two or three years later they peak in abundance."

This scenario is remarkably similar to what John Fitzpatrick described when he spoke at the Bird Conservation Network Conference in November 1999. Fitzpatrick, Director of the Cornell Lab of Ornithology, told a fascinating story of Florida scrub-jays that can be applied to what's happening to some birds in the Chicagoland region, indeed the whole state. "The birds," he says, "are telling us something about the land and our role in managing the land."

Fitzpatrick's research at the Archbold Biological Station in Florida showed that fire temporarily destroyed habitat for the rare scrub-jays, but that lack of fire over the long term permanently destroyed their habitat. A natural lightning fire occurred in 1989 burning 400 acres. For the next three-to-four years, the Florida scrub-jay did not use that land for breeding. But plants not seen for 30 years reappeared, along with a larger community of insects, and soon, the scrub-jays returned, breeding and producing young more successfully than in areas that had not burned. "This is a message for Illinois," says Fitzpatrick. "Sometimes birds have to go next door (while lands regenerate). But do we have a next door for them to go to?"

"Today, birds' options are severely limited," says Herkert, whose research shows that a given species of grassland bird reproduces best when it has a large acreage of one type of grassland in which to breed, for example, medium-height mesic prairie. That may be related to predation rates, he says. "We're finding predation rates in grassland birds are very high, significantly higher than woodland birds," he says. "Some 5-10 percent of the nests we studied were lost in any given day." All told, 80 percent of the nests were lost due to predators before the birds fledged. The state-endangered upland sandpipers had the highest nest success rate among the grassland bird breeding at Herkert's study sites, approximately 65 percent. "Perhaps it's because their eggs are larger," he says, "and the smaller snakes and mice can't get them."

"If we established one or two 1,000-acre grasslands, such as one that consists of shorter grasses, predation rates might drop," he says, "and then the area might attract more birds, and the birds would produce more young."

And what about shrubland birds? Herkert says grassland birds do not tolerate shrubs, yet if all the shrubs are removed at Midewin, birds that breed there, such as Bell's vireo and loggerhead shrike, would suffer. Herkert thinks Midewin is large enough for both grassland and shrubland birds to coexist. "We're finding shrubland birds don't need as big areas as grassland birds do," he says.

"Small shrublands embedded in large grassland seem to attract them most. The nesting success of shrubland birds is also typically higher than grassland birds," Herkert adds. "The population of loggerhead shrikes at Midewin has been remarkably consistent. That's because there's great habitat. Shrikes tend to do well with grazing. And there's been a history of grazing on the land. That's a big issue at Midewin." If cows are taken off, and not replaced by bison, as some have proposed, then the birds that depend on grazing, like loggerheads and upland sandpipers, could suffer.

As grasslands undergo changes that either hinder or help breeding birds, so do wetlands. For five years, Dr. Charles Paine, a wildlife research biologist at the Max McGraw Wildlife Foundation in East Dundee, and his colleagues have been gathering data on abundance and nest productivity of wetland birds in northeastern Illinois. Paine's initial findings seem surprising at first, especially since 40 percent of the endangered and threatened birds of the state are wetland species. For example, least bitterns are more abundant than most people thought. One year, Paine and his research team recorded 12 least bittern nests at a 35-acre wetland at Cuba Marsh in the Lake County Forest Preserves. In addition, they found nesting success among threatened and endangered wetland birds was high — higher, in fact, than the rates observed among savanna, grassland, and woodland birds in Illinois. In the first three years of their study, they found nest success was 66 percent for yellow-headed blackbirds, 57 percent in common moorhens, 65 percent in pied-billed grebes, and 80 percent in black terns.

In the next phase of his study, which began in 1998, Paine chose 90 wetlands from randomly selected 1,400 good-quality marshes. He then recorded numbers of birds on the marshes once every three weeks, and nesting productivity at 18 sites. That data also showed nesting productivity is fine on good quality marshes.

So if nesting success is high, why are wetland birds still declining here?

"Most of our threatened and endangered marsh birds are dependent on hemi-marsh conditions," Paine explains. "Marshes tend to run through cycles from fairly dry dense stands of emergent vegetation, mostly cattails, to rising water levels in which the emergents can't survive and get drowned. That creates an interspersion of water and emergent vegetation. The ideal is 50 percent water/50 percent emergent vegetation, thus the term hemi-marsh. These conditions seem best for many wetland birds including the state-endangered black tern and yellow-headed blackbird and the state-threatened least bittern, common moorhen, and pied-billed grebe."

Until 50-100 years ago, enough marshes and wetlands existed so if one was not at the hemi-marsh stage, birds didn't have to fly far to find another one that was suitable for breeding. In short, enough habitat existed for them to adapt to natural changes both within the marsh and due to outside influences such as drought or excessive rainfall. Today, that's no longer true: northeastern Illinois probably has only one percent of its pre-settlement wetlands, and many of them are becoming degraded. The loss of wetlands coupled with human influences — cutting roads through marshes, putting subdivisions next to marshes that over time change the water flows and levels, and introducing non-native carp that stir sediments — can all render a marsh unproductive for breeding birds, especially the rare ones.

Paine poses this question: "What will happen if the remaining marshes continue to deteriorate? Do we have enough marshes to get birds through the hard times?"

Then consider the needs of individual species. "Black terns have very specific requirements," says Paine. "Only two breeding colonies remain in Illinois, one of them at Broberg Marsh in Wauconda. Black terns require wetlands where vegetative mats form. Broberg has a mix of cattails and bulrushes and arrowheads. When the plants die, they form peaty mats. But this is an ephemeral condition. At Broberg, the terns have been stable in the last five years, but are there other marshes nearby where they could nest if that marsh changes? What are the chances of them finding other suitable habitat?"

Paine speaks energetically and honestly, painting bleak pictures of some birds such as the American bittern, which may never re-establish its historical population in Illinois, as well as painting optimistic pictures of what humans can do to correct past mistakes. Among researchers and scientists, he is one of the more avid birders, reveling in the thrill of hearing a pied-billed grebe emit its maniacal courtship song across the billowing cattails. Paine thinks the best way to sustain wetland bird populations in northeastern Illinois is to manage them by placing structures in the wetlands that can alter the water levels as would have occurred naturally a century ago. "There are real opportunities here for restoration," he says, noting the change in hydrology in a low spot in a farm field in Kane County created perfect conditions to attract breeding yellow-headed blackbirds.

In 1995, Brad Semel, a biologist with the Illinois Department of Natural Resources (see our profile of Semel in this issue), drastically lowered the water level at Black Tern Marsh in Moraine Hills State Park in early summer because static water levels in the marsh had rendered it unsuitable for breeding birds. "Brad took a lot of grief for doing that because birders didn't see yellow-headed blackbirds that year," says Paine. "But it killed off all the carp and by late July, bur reeds and bulrushes were over your head and for the next couple of years following, it was really productive for wetland birds," he says. The yellow-headed blackbirds were back, and last summer, they, as well as common moorhens and pied-billed grebes, bred at the McHenry County site. "But they'll have to keep managing the area, if the marsh is to continue cycling properly," Paine says.

When it comes to savannas, the amount of open canopy is what determines a breeding bird's success, says Jeff Brawn. An expert in statistics and study design, Brawn has done some of the first studies of the birds of our open woodlands and savannas.

Brawn's analysis of data from research in the Palos Preserves in Cook County shows that open oak canopy with some understory shrubs is the best habitat for a suite of birds. Indigo buntings, red-headed woodpeckers, Baltimore orioles, and rose-breasted grosbeaks are more abundant in restored areas, he says. Eastern bluebirds also prefer open wooded habitat for nesting. And even more importantly, the reproductive success is higher for grosbeaks, red-headed woodpeckers, eastern wood-pewees, and indigo buntings in restored areas compared to closed canopy woodlands. While closed forest birds need contiguous acreage, savanna and open woodland birds seem not to need that. In fact, they can breed successfully even if their nests are near trails, he says.

Brawn says wetland and grassland birds are in worse trouble in the Chicago Wilderness region than are savanna birds, but that doesn't mean we should ignore the savannas.

Some savanna species are declining nationwide. For example, the red-headed woodpecker is declining dramatically, perhaps because it has more specific needs than some of its other savanna cousins. Red-headed woodpeckers need oak-dominated lands, with a high production of acorns. They also need dying trees for nesting sites.

Brawn hopes to begin a more detailed study of the red-headed woodpecker to discover how restoration helps increase nesting success. Is it because fewer predators exist in restored areas?

In spring, red-headed woodpeckers, bobolinks, yellow-headed blackbirds, upland sandpipers, and many other rare breeders return to the Chicago Wilderness region to look for a place to become a parent. If researchers, land managers, and concerned citizens understand the complexities of these birds' habitat needs and how they fit into the continuum of this great region we call Chicago Wilderness, then perhaps these birds will brighten our skies and spirits for generations to come.

See also "Bird Monitoring Pays Off"

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