By Jerry Sullivan
A few years ago I assembled a list titled "Putative Birds of the Savanna." It was a sort of speculative first attempt at figuring out what sort of bird communities lived in the varied landscape of open prairies interspersed with oak groves that was a major feature of presettlement Illinois.
The list, like the landscape, had to be reconstructed. History has not been kind to our native savannas. Plowing, grazing, logging, the introduction of exotic species, fire suppression, and landscape fragmentation have combined to nearly annihilate the savanna.
Birds have reacted to this destruction in quite different ways. Some of the birds on my savanna list--long-eared owl, loggerhead shrike--have followed the plant communities to a place on the endangered list. Others--robins, northern orioles--have found that suburban neighborhoods, city parks, golf courses, and cemeteries serve them as well as bur-oak groves.
So my list had a schizoid quality. It combined a number of species from the endangered and threatened list with species that are common as dirt.
When I wrote the list there was little opportunity for testing its accuracy. "Yes! We have no savannas" could have been our state song. But lately ecological-restoration projects have been helping the native landscape make a comeback. I am deeply involved in these projects--both professionally and emotionally--so I have a strong rooting interest in them, and I am always happy to see evidence of their success. I am also hoping that reality will vindicate my list.
The biggest restoration project in the Chicago area is at Swallow Cliff Woods in the Palos area. On more than 800 acres there the Forest Preserve District of Cook County is carrying out what is called a landscape-scale restoration project. "Landscape scale," as far as I can figure, means "really big."
In presettlement times Swallow Cliff Woods was an ecotone--a border--between tallgrass prairie and forest. Fire was the controlling force in the landscape. Burning from level ground to the south and west, the fires maintained prairie on the southern part of the area. Toward the north the ground gets rougher, creating an obstacle to the fires. So from south to north we have prairie, open groves of bur and white oak, a rather dense red-oak woods, and on the cool north-facing slopes of the "cliffs" themselves a sugar-maple/ basswood forest. If you graphed these communities with "fire dependent" at one end of the scale and "fire sensitive" at the other they would be arranged exactly as they are on the ground at Swallow Cliff.
Like nearly all of northeastern Illinois, Swallow Cliff Woods has been fire starved for years. With no fires to help sustain the native communities, an exotic shrub called smooth arrowwood invaded both the prairies and the woodlands. At its worst, it grew so thickly that people studying the area in preparation for the restoration project had to crawl along on their bellies, and it sometimes took them an hour to travel a couple hundred yards.
We have now cleared the arrowwood from a substantial part of the site. The huge old bur and white oaks are visible again, and conditions are such that we can hope that they'll reproduce--something they could not do when the arrowwood was densely shading every square foot of ground.
It is certainly too soon to tell what kind of effect the restoration will have on the birds of Swallow Cliff, but we do have a bit of evidence that my savanna list was at least partly right. We can start with the summer tanager. A male has been present at Swallow Cliff since late May. Both of the tanagers of eastern North America--the summer and the scarlet--show a strong affinity for oak woods. Summer tanagers are the more southerly species--the Swallow Cliff bird is probably 100 miles north of what is generally regarded as the limit of its range--but they are also more inclined to like open groves and small patches of trees. In southern Illinois they sometimes nest in lone trees along country roads. Scarlet tanagers--which also nest at Swallow Cliff--seem to prefer larger, denser woodlands.
The summer tanager is our only totally red bird--male cardinals have a patch of black surrounding their beaks, and scarlet tanagers have glossy black wings and tails. The Swallow Cliff bird was still singing a week ago, which could mean that it has no mate. Most mated birds have stopped singing by this time. However, we did see a female summer tanager there in May, and everything is late this year.
The eastern bluebird is another species on my putative savanna bird list that has shown up at Swallow Cliff this year. My favorite is a male that has been hanging around the picnic grove. He's a lazy man's bird. You can sit in your car and watch him actively feeding in the lower limbs of the white oaks.
Bluebirds were a species of concern for many years, but locally at least they seem to be coming back. Just five years ago there was only one nesting location for this species in all of Cook County. Now we have several, and I am happy to say that the sites of ecological-restoration projects are particularly attractive to these birds.
We've got orchard orioles at Swallow Cliff too. Our common oriole in this part of the world is the familiar orange and black northern oriole. This is the bird that used to be called the Baltimore oriole because its colors were the same as those on the coat of arms of Sir George Calvert, the first Lord Baltimore.
Orchard oriole males are chestnut and black rather than orange and black, and the females are pale green above and dull yellow below. Orchard orioles shun the deep woods. They like more open situations than their orange and black cousins, and they tend to build their nests somewhat lower than northern orioles.
We also have a sighting of a ruby-throated hummingbird at Swallow Cliff, and a nest was found right next door at McClaughry Springs Woods. I would love to find a hummingbird's nest. You would have to be lucky to discover one--the nests are not much bigger than a walnut half. They are made of down from thistles or milkweeds bound together with spiders' silk and decorated with pieces of lichen. The nest is just big enough to hold two eggs, each about the size of a Navy bean.
Hummers are polygynous. The males defend a feeding territory that may be no larger than a single tree or tall flowering shrub. After copulation the females build the nest and rear the young on their own. Female birds maintain breeding territories from which they drive other females and males as well.
Open woods--the sort of open woods that were typical of the native landscape of Illinois--are the favored habitat for these tiny creatures. They do need flowers, after all. They feed on nectar and on the tiny insects that flowers attract. In deep woods flowers tend to bloom in spring before the leaves open. By midsummer the forest floor has few flowers. Open woods and savanna groves have enough light to support a succession of flowers that bloom throughout the summer, making them much more likely to attract hummingbirds.
One year's data is too slim a thread to hang any heavy conclusions on, but I do feel a certain satisfaction at the possibility that my predictions about the effects of restoration will come true. I will miss "putative" if I have to change the title of my list to plain old "Birds of the Savanna." However, I think I'll be able to bear the loss.