Birds of the Shrublands
By Judy Pollock
Shrublands once moved across the land in response to fire, and shrubland birds thrived. Bringing back this habitat of impermanence may be the next big thing in conservation.
Photos: Richard Day/DI
My favorite day in the field is a day in June when the birds invite me into their living room. I pull up a “chair” at the edge of a shrubby meadow and enjoy myself in plenty of good company — indigo buntings carrying worms into the nursery, catbirds mewing from the fridge, rumpled song sparrows peering from a footstool, and a cuckoo toc-toc-tocking from just outside the window.
The birds make these places so convincingly their own each summer that it’s hard to believe their homes are not at least as permanent as mine. Yet the shrubland I am observing on this perfect day may be utterly changed in just a few years, with most of its birds gone. Unlike so many disappearing habitats, though, this is all part of a natural cycle.
That cycle hinges on disturbance. If a fire roars through, or a brush clearing crew, and if the site is large enough, grassland birds may replace the shrubland birds, which will search for more suitable homes elsewhere. If left undisturbed, the landscape of shrubs will transition to thickets and forests, attracting yet a different set of birds.
For thousands of years, the grand fires that annually redeemed the grasslands also imparted a rhythm to shrublands. “Barrens” of stunted oaks, and thickets of hazel, plum, crab, hawthorn, dogwood, viburnum, blackberry, rose, and others bounded and shuffled around the landscape in response to fire. Other disturbances — beaver dams, major floods, and windstorms — also played a part.
Once the large fires were stopped, we lost our native shrublands along with our grasslands. Large oak barrens and thickets of hazel are a thing of the past.
Despite these enormous changes, most shrubland bird species are still present in the region — a testament to their adaptability. Today, they are just as likely to be using invasives such as honeysuckle, buckthorn, or Osage orange as they are native plum or viburnum. While some animals such as butterflies will only use one specific plant species, birds are less picky, responding to the structure of shrubs and shrublands — if a plant’s got the right shape, size, height, and location, it will probably serve for shelter, lookout, nest site, and camouflage from predators.
But numbers of many shrubland species are declining, and some of these declines are beginning to cause real concern. In fact, only grassland birds as a group are declining more rapidly than shrubland birds across the United States.
Photos from left: Dave Jagodzinski, Richard Day/Daybreak Imagery, Kanae Hirabayashi.
Some species, such as the field sparrow, are rapidly declining yet still very common. Despite substantial population drops — 2.8 percent per year since 1966 in Illinois, and similar declines nationally — the field sparrow is still easy to find in the right habitat. The brown thrasher and eastern towhee have similar patterns. One reason for the national declines is the change in land-use patterns in the East, as farms are abandoned and forest closes in. That places the burden for maintaining these habitats on the Midwest, an historic stronghold for these birds. Although these species are in no immediate danger, the declines here are troubling.
Others of our threatened shrubland birds are not so common, and have made it onto various national watch lists. These watch lists weigh declines, threats, and the importance of the region to the species in order to advise us which bird species would be the best focus for our conservation energies. The willow flycatcher, Bell’s vireo, blue-winged warbler, black-billed cuckoo, orchard oriole, and loggerhead shrike are all mentioned on the U.S. Fish and Wildlife Service’s List of Birds of Conservation Concern for our region.
The disappearance of habitat accounts for some of the decline in Chicago Wilderness, but medium-sized predators (known as mesopredators) also place enormous pressure on the low-nesting shrubland birds. Raccoons, opossums, snakes, squirrels, jays, and crows all eat eggs and young birds, and they make shrublands a part of their regular beat. The highly fragmented landscape and lack of large carnivores in our expanding metropolis provide perfect conditions for them to saturate shrublands.
Photo: Ray Mathis.
Studies have shown that as coyotes return, songbird populations increase because the coyotes control the mesopredators. Humans also can play an important role in restoring the balance that was upset when we lost our large predators. Chris Whelan, an ornithologist at Midewin National Tallgrass Prairie, and others believe that when the price of raccoon pelts drops below a certain level, our local songbirds suffer — apparently, the collar counties support a number of raccoon trappers. Deer control is important, too. Studies in the East show that habitat destruction caused by deer overpopulation can take a heavy toll on birds of shrubby woodlands.
Right now, it is uncommon to find a local restoration plan that contains any serious planning for shrubland birds. But if our local history of prairie and savanna restoration is any guide, these declines will serve as a call to action, and we will find abundant local talent ready to take on the challenge.
Forty years ago, we were planting forests in prairies because we believed that was good conservation. We’ve come a long way since then. Research and experience has guided us to protect remnants and restore new prairies, wetlands, and savannas. They have all been pioneering ventures for which there were no instruction manuals. Sometimes existing shrubland habitat (especially of nonnative species) has been destroyed in the process, to the dismay of bird lovers. Yet around the region, shrublands large and small are now beginning to show up in restoration plans, including at Montrose Point in Chicago and Hickory Creek Barrens in Will County.
The Forest Preserve District of Cook County, along with Audubon, is preserving some large fields of grassy shrubland in the 4,000-acre Spring Creek preserves in South Barrington while converting others back to grassland. And at Foley’s Fishing Pond, a small Highland Park, Illinois, preserve that is a favorite of migrant birds, Natural Areas Coordinator Rebecca Grill teamed up with Donnie Dann, Audubon, and other volunteers to replace invasive buckthorn with native shrubs. As we learn and experiment, we can make these impermanent habitats a permanent part of our planning.
Pollock is director of bird conservation for Audubon–Chicago Region.
Shrubland Bird Hotspots
Volunteers regularly monitor 95 sites that support shrubland birds of concern. Here are a few sites that have had big tallies:
The Palos preserves, especially John Duffy Preserve, Hodgkins, IL
Midewin National Tallgrass Prairie, Joliet, IL
Herrick Lake Forest Preserve, Wheaton, IL
Spring Creek Headwaters, South Barrington, IL
Hickory Creek Barrens, New Lenox, IL
How to Host a Shrubland Bird
“It takes a certain amount of creativity to keep things in a shrubby state. You have to lay off — but not too much,” says University of Illinois’ Jeff Brawn, who coauthored a series of studies with recommendations for managing local shrublands.Here are a few of his team’s guidelines:
Know your shrubland type. The word shrubland can encompass anything from a lone plum thicket in a prairie to a hawthorn-filled woodland opening, and birds use the whole range. The loggerhead shrike needs thorny trees in fields of short grass, while gray catbirds are found in the densest thickets.
Plan longer disturbance cycles. Left alone, shrubland habitat eventually grows up and goes away. At Midewin Prairie, Chris Whelan observed Bell’s vireos move into a field when the vegetation got to be just the right height — three years later they moved out. An ideal shrubland plan would have several sections that would be mowed or burned on a rotating basis. Brawn says to try a disturbance cycle of about ten years.
Leverage small open spaces. While some shrubland bird species need lots of habitat, many will do just fine in small spots. A prairie of less than 40 acres will likely not attract grassland birds. Yet allowing a few clumps of shrubs to grow in one of the wetter spots of that prairie creates critical habitat.
Please rare birds. Brawn found that our rarer shrubland birds, such as Bell’s vireo and willow flycatcher, tend to favor wet grassland with clumps of shrubs and small trees, a habitat he recommends as an important restoration target.
Bring back lost shrubs. Some of our native shrubs are becoming downright hard to find. The scattered remains of our once-abundant hazel thickets are heavily browsed. Squirrels make off with the nuts. The Morton Arboretum’s Marlin Bowles, who has reintroduced hazel at Hickory Creek Barrens, found that it burns back to the ground and needs at least a three-year fire cycle. Setting up nurseries for such dwindling species (and protecting them once planted) may be necessary.
Discourage midsize maulers. Brawn found that the chances of a shrubland bird’s brood being destroyed range from 70 to 95 percent. The main culprits are raccoons, squirrels, and possums. Homeowners can help by putting no food other than tiny amounts of seed on the ground, and by providing seed in feeders only available to birds. Removing hedgerows in natural areas helps, too. These serve as lanes that bring edge-loving predators into otherwise inaccessible areas.