For the past few weeks I’ve been spending as much time as I can afford studying the birds of the oak savannas of the midwest. This is a bookish enterprise. All but a few tiny, degraded remnants of our native savannas vanished before the end of the 19th century, so there is no place I can go to actually see a savanna and the birds that live in it.
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Ecology, like every other human endeavor, has its fashions, and right now the oak savanna, the mixture of grassland and trees that covered a large part of presettlement Illinois, is a fashionable ecosystem. It also represents a second stage in our rediscovery of the native vegetation of the midwest. You could say that stage one began about 60 years ago, when botanists at the University of Wisconsin started trying to create a native tall-grass prairie in the university’s arboretum. It accelerated 30 years ago when Robert Betz of Northeastern Illinois University, working with Floyd Swink and Ray Shulenberg of the Morton Arboretum, began to study prairie remnants in the Chicago area.
Twenty years ago Betz persuaded the Nature Conservancy to buy the Gensberg-Markham Prairie, the largest remnant in the area, and his efforts had a lot to do with making public conservation agencies aware of the need to acquire prairie lands for preservation. Betz, Shulenberg, and Swink also played key roles in initiating the now-flourishing work of prairie restoration around Chicago. Some of that work helped arouse interest in the oak savanna.
There is a temptation to focus on the oak groves when we think about savannas, since they seem like the most distinctive feature of the landscape. But the essence of a savanna is variation. There were indeed shady groves of tall oaks whose broad crowns formed a nearly continuous canopy of leaves. There were also large patches of prairie dotted with scattered single trees. There were groves that covered a single acre and groves that extended over hundreds of acres. There were groves of big old trees and groves of small young trees. And there were places called brush prairies where low shrubs of dogwood and blackberry and hawthorn were the dominant plants. Each of these varied landscape types would have had its own distinctive group of birds, so the list of savanna birds has to include them all.
There are other brush birds with a greater need for trees. House wrens need at least one dead tree to provide a nest hole, and indigo bunting males like to sing from the tops of the highest trees around. We can imagine them at edges where grove met prairie.
As complicated as my job of historical construction is, I am supported by two thoughts. One is that despite the destruction of our native savannas, nearly all the birds that once inhabited it are still around. Their numbers and their geographic ranges may be much reduced, but they have not disappeared. Restoration efforts, combined with better management of lands where significant portions of savanna ecosystems remain, could bring them back.
