from two acres to seventy

The high quality Somme Prairie is increasing from two acres to seventy acres. Hundreds of vulnerable species that have been hovering on the edge of oblivion, because of fragmentation, now may have a sustainable future.

If you had stood on the highpoint of Somme Prairie two hundred years ago (or 2,000 years ago), you would have seen rich treeless grassland rolling majestically to the horizon – looking south, or west, or north. To the east, you would have seen a mile of prairie backed up by savanna and woodland on the moraine. Today from that same spot, off to the south, west, and north, you see businesses, a post office, a dog park, roads, and homes for people. Some of those people are glad a prairie survives and can recover. 

Forty years ago at Somme, two acres of very high quality prairie remained, in scattered patches. Most plant and animal species are not sustainable in a two acre habitat. The prairie species, you can imagine, were shivering in fear. When we first started to rescue biodiversity here, the surrounding brush was gobbling up more prairie every year. In the absence of fire, brush kills every grass, flower, bird, butterfly, nematode, and fungus of the prairie. For forty years, volunteers cut shrubs and trees. Brush tried to grow back as fast as we could cut it. We concentrated on the biggest and best quality openings. We lost some, as brush obliterated them. But most of those remnant patches recovered bit by bit, year by year. Yet, we didn’t have as many troops (or as much fire and seed) as we needed. It was taking too long.  

When we first saw Somme Prairie, the best parts looked like this. I took this photo standing in the edge of one brush wall, looking past a few shrubs and out into a high quality prairie opening. Behind the prairie, you see a few trees and a wall of shrubs. Behind that wall is another opening (hidden behind the brush), and then further back, bigger, taller brush again. 

By 2010, Steward Laurel Ross and the volunteers of the North Branch Restoration Project had about thirty acres of prairie under restoration. But forty acres were still under shade. Volunteers are mighty, but we are spread over many sites. Thousands of generous friends and neighbors have contributed here, from a few hours to hundreds of hours each, but we have only been able to do so much. 

Increasingly in recent years, Forest Preserve staff and contractors have focused resources on Somme. In 2014, President Preckwinkle and the Forest Preserves board approved its “Next Century Plan.” By August 2020, according to the current plan, there will be no brush in Somme Prairie. This is huge.

On September 20, 2018, conservationists met to refine bird conservation elements of the plan. Shown here, from left, are Laurel Ross (volunteer steward), Dr. Doug Stotz (ornithologist, Field Museum), Becky Collings (Senior Resource Ecologist for the Forest Preserves), Debbie Antlitz (Forest Preserve ecologist for the northeast region), and Dr. Jim Herkert (ornithologist, Illinois Audubon Society).  
(See Endnote 1.)

This work is a model of collaboration. Forest Preserve staff, volunteers, partners, and scientists work together. (See Endnote 2.) The following is a summary of the discussions the bird conservation planning group had that day. Bird conservation was just one part of the overall plan. (See Endnotes 3 and 4.)

The most important overall conservation goal for the 70-acre Somme Prairie is the restoration of its original prairie community – as large and fully diverse as possible. The birds are just one part of that community, but our main goal today is to focus on the birds part.

The basic bird-conservation objective is a large and unbroken grassland of good structure for breeding prairie birds, especially Henslow’s sparrow, dickcissel, sedge wren, savanna sparrow and possibly meadowlark.

Currently no prairie birds nest in Somme Prairie. But with increasing size and quality of habitat, breeding birds can be expected, in time. Currently, some prairie species breed at Air-Station Prairie (a few miles to the south) and Willow-Sanders preserve (a few miles to the southwest).

The rare Henslow’s sparrow, if you get a good look, has a greenish head and rufous wings. It’s considered a high priority for conservation, as its habitat is the eastern tallgrass prairie. Currently much of this species survives on agricultural lands – in temporary habitats. Populations in preserved grasslands may be crucial to this bird – and to the quality of the grassland.

Grassland areas the size of Somme may have significant contributions to make. There are potentially about 100 acres of quality prairie habitat here, if we remove the brush barrier that separates Somme Prairie from formerly contiguous habitat in Somme Prairie Grove to the east. Recent studies suggest that the value of smaller urban grasslands can be higher than previously thought. The proposed work at Somme could combine with, inform, and inspire similar work at scores of existing and potential grassland bird breeding sites in the Chicago Wilderness region.

Would we be wise also to save shrublands here? No. For a site of this size, a single focus on grassland bird habitat is far superior to a compromise that would attempt to restore both grassland and shrubland. Other sites (including the adjacent Somme Prairie Grove) are successful and superior for shrubland bird conservation. More importantly, shrubs are a main threat to grassland birds – and challenging to manage. The agreed-on best strategy here is for the entire site to be restored as prairie.  

In the photo above, the 7.5 acres of invading trees and brush were mostly removed in winter 2020. The last 4.8 acres will be cut as soon as dry or frozen ground permit - possibly August 2020. The brush and trees removed by contractors in 2019 have white hatched lines. The pale areas are original and recovering prairie. The darker areas are trees, brush, weeds, or other prairie-destroying invaders. Even after the brush has been cut, the “seeds and weeds” stewards have a lot of work to do. 

After trees and brush have been cleared, there’s still a lot of work to do to eliminate such malignant and habitat-destroying invasives as crown vetch, reed-canary grass, purple loosestrife, and teasel.

But the major first-step threat here is shrubs and trees. When just a foot or two tall, shrubs are not in themselves a detriment to the grassland birds. But, in two or three years, between burns, woody plants with well-developed root systems tend to grow sufficiently to shade out the species of grasses and other conservative plant diversity that make for successful grassland bird nesting habitat. The plan is to treat shrubs, trees, invasive weeds, and seed planting in a step-by-step process. (See Endnote 3.)

Another principal threat is aggressive forbs such as tall goldenrod (Solidago altissima) and saw-tooth sunflower (Helianthus grosseseratus). These and other rank species can create a vegetation structure that blocks or retards the desirable establishment of natural prairie. Such “thug” vegetation is also not nesting habitat for most grassland birds. These areas frequently do not burn under the moderately flammable conditions of most controlled burns, as the fuel quality is low. The rank species are thought to obstruct better quality vegetation by shading it out and possibly by emitting chemicals from their roots that inhibit the growth of other species. One solution to this problem that has been effective in some cases is to seed diverse prairie vegetation and then mow the rank growth when it becomes too dense for the survival of desirable seedlings.

The new Forest Preserve plan (above) shows Somme Prairie outlined in red, Somme Prairie Grove in orange, Somme Woods in yellow and green, and Chipilly Woods in blue. 

9.    We next visited the 85-acre Somme Prairie Grove (adjacent to the east) and considered relationships between it and Somme Prairie. A coordinated plan for the two preserves now makes more sense. The prairie portions of these two preserves are divided from each other by the North Branch of the Chicago River (which flows unnaturally in a deep, straight ditch) as well as by the Metra railroad tracks. Neither the ditch nor the tracks would impede prairie birds from using both sides as one larger grassland. (More on the opportunities here will come in a later post.)

Most prairie birds have lost 90% or more of their numbers. This dickcissel could one day return to the Somme preserves. The five bird species likely to return here feed their young mostly on insects that few birds are now eating. The return of prairie birds may thus restore a component of
natural balance to the prairie here. 

A special feature of Somme is a continuum from quality prairie to quality savanna and shrubland to quality woodland (as we go east from Somme Prairie to Somme Prairie Grove and the adjacent 450 acres of Somme and Chipilly Woods. The restoration of such a rare continuum would benefit birds, plants, invertebrates, herptiles, and the ecosystem generally. (See Endnote 4.)

Relative conservation priority of shrubland, savanna, and prairie birds: They’re all important, but the prairie species are a higher priority, especially for Somme Prairie. Birds of shrubland and savanna are second priority.

We were entertained during our walk in Somme Prairie by a merlin (an uncommon mid-size falcon) which was being mobbed by blue jays in between bouts of the feisty merlin harassing a kestrel (a smaller falcon) and a sharp-shinned hawk. Perhaps this performance was a good omen for our bird conservation planning efforts here.

Then, one last thought:

Will Somme Prairie someday truly revel in 70 acres of very high quality prairie? No one knows. No one has ever seen very-high-quality prairie restored. But even “good” prairie would be a blessed improvement over the formerly advancing brush – and many plant and animal species are already thriving in some of the restored areas. How fast and how much the ecosystem can recover will be a fascination and inspiration to experience over the years ahead.  

Endnotes

Endnote 1

The planning session on bird conservation was assembled by Becky Collings and Laurel Ross. The full roster for that field meeting included: 

Forest Preserve staff: Becky Collings and Debbie Antlitz

Bird conservation and ecology: Jim Herkert (Illinois Audubon), Doug Stotz 

and Dave Willard (Field Museum)

Somme Prairie stewards: Laurel Ross and Lisa Culp Musgrave

Somme Prairie Grove steward: Stephen Packard

Endnote 2

In case "model of collaboration" sounds Pollyanna to anyone, let me hasten to assure you that "collaboration" does not mean an absence of problems. It means we all pitch in, respect each other, and work problems out, as best we can. Good work goes forward, and we all contribute. 

Endnote 3

Photos showing step by step: 

Most of what was rich prairie long ago had degenerated into solid brush, as seen behind the sign below. 

The transformation of Somme Prairie became visible from Dundee Road on December 13th, 2018 with step one. A large "mower" chopped up the understory brush, as shown below: 

Step one, as seen from Dundee Road, looking north, with the small brush clearing just completed. The existing prairie is that pale horizontal line behind the trees.
Photo by Forest Preserve resource project manager Troy Showerman.

This is the machine that did the work.
Photo by Troy Showerman.

Above, from the Post Office parking lot, you see the mowed area compared to a still untreated area on the right. One of the next big challenges will be to keep the brush from growing back by herbiciding brush re-sprouts and seedlings, done during the 2019 growing season. The rest of the invading trees shown here were cleared when the ground was frozen solid enough to support heavy equipment, in winter 2020. Starting in fall 2019 and continuing for some years, rare prairie seed is being broadcast where the brush was cleared. Staff and stewards will combat new infestations of invasives. The ecosystem is temporarily in an "intensive care" stage.

Some day, the goal is, the whole 100 acres will once again look like this: 

Endnote 4

Does this post make too much of a fuss over birds, compared to the rest of the ecosystem? Yes, but. Birds often rightly get extra attention because the data for them is especially clear and strong. We know better how big preserves need to be (and what vegetation structure needs to be) for bird conservation than we do for most other species. Part of the reason for that, is that people have done more research on birds, in part because they have more constituency and support. Birds bring more supporters to conservation efforts than do rare walking sticks or snakes.

As conservationists, we care equally for now-rare ants, weasels, slime molds, etc. - but we have less complete data on their conservation needs. But there's data for many species in many habitat types that confirm the value of larger habitats. Thus, restoring size and quality for birds will likely help many other plants and animals for which we have less detailed knowledge.

Midwest invertebrate expert Dr. Ron Panzer, who studied Somme years ago, published data that strongly supported the value of large habitats and higher quality vegetation for invertebrate conservation. But he cautioned against relying on size and vegetation alone. Burn regimes and other features may be equally or more important. Conservation will be on increasingly solid footing as we learn more about the needs of more and more species.

Credits

Beyond those already mentioned in this post, as always, there are many more who deserve recognition. To mention a few, let’s acknowledge:

John McCarter, Wendy Paulson, Arthur Velasquez, and Eric Whitaker: co-chairs of the Next Century Conservation Plan Commission – along with the scores of people who contributed to the planning process. And forest preserve President Toni Preckwinkle who coordinated the adoption of the plan.

Dozens of Forest Preserve staff and contractors as supervised by John McCabe who has much upgraded the professionalism of the Forest Preserve’s Resource Management Division.

Volunteers by the hundreds, including Somme Prairie co-steward Lisa Musgrave and Eileen Sutter who, with many leaders and volunteers, has headed up the seed-gathering crews of the North Branch Restoration Project.

Jeanne Muellner who took the great photos of the Henslow’s sparrow and the dickcissel at the Orland Grassland, where they both thrive in restored habitat.

Thanks for proofing and edits of this post to Becky Collings, Troy Showerman, Lisa Musgrave, Eriko Kojima, and Kathy Garness.

References

For an introduction to Somme Prairie Nature Preserve, check out captions and photos of Somme Prairie from a walk in late May - and a set of very different photos and comments from July.

The Next Century Plan of the Forest Preserve District of Cook County  

Summary of the Somme Prairie plan

http://fpdcc.com/preserves-and-trails/plans-and-projects/somme-prairie-nature-preserve-habitat-restoration/

Henslow’s sparrow biology and conservation

Chicago Region “Bird Conservation Network” birds of concern

https://www.bcnbirds.org/trends13/concern.html

The birds of conservation concern of the Somme preserves:

Woodland birds regularly breeding in Somme Woods include red-headed woodpecker, American woodcock, and northern flicker.

Shrubland and savanna birds regularly breeding in Somme Prairie Grove include brown thrasher, willow flycatcher, field sparrow, American woodcock, northern flicker, and eastern kingbird. 

Prairie birds currently breeding in Somme Prairie include none at all, for decades. The pitiful fragments of surviving prairie are too small. Thanks to all who are helping the recovery of the plants and animals of Somme Prairie.