My survey of the breeding birds of Somme Woods Forest Preserve is drawing to a close. The birds that will nest there this year are already sitting on eggs or feeding young. For some species, the young are out of the nest and the parent birds are preparing to nest again.
I guess I can say the results of the survey are mixed. I got a few species I didn't expect and missed some I had hoped for. I did not find nearly as many nests as I had hoped to discover, but I did at least learn a few things about how to go about searching for nests.
The area of Somme Woods I was surveying lies west of Waukegan Road and north of Dundee Road at the far northern end of Cook County. I chose it as a survey area because it is one of the preserves being restored by volunteers from the North Branch Prairie Project.
Before settlement began in Illinois, the area I've been surveying was split by the west fork of the north branch of the Chicago River. (The river is still there, although now it has been reduced to a narrow, steep-banked ditch.) West of the river, the land was flat and dominated by prairie. East of the river, on the Deerfield Lobe of the Lake Border Moraine, the rolling landscape was principally oak savanna.
By the time the Cook County Forest Preserve District began to acquire the land in the 30s, farming and grazing had destroyed most of the native vegetation. A small patch of virgin prairie remained west of the river. East of the river, a few giant oaks, trees that began their lives when the Pottawatomi still lived around Chicago, had survived.
After the Forest Preserve took over the land, shrubs--especially the invasive alien called European buckthorn--and pioneering trees like ashes and box elders began to expand their presence. Eurasian grasses and wildflowers took over most of the old fields.
The North Branch Prairie Project volunteers have spent the past 12 years reversing the trend that began with settlement. They are removing the aliens, replanting native species, and restoring fire to its former role as a major actor in the ecosystem. My survey of breeding birds is part of a long-term effort to find out what effect the changes in the plant communities will have on the bird populations.
So far those effects seem small but noticeable. Consider, for example, the woodpeckers. Somme Woods should be woodpecker heaven for the next several years. The NBPP people are girdling all those invasive trees--the box elders and ashes. Girdling involves cutting away the living tissue just under the bark and severing the connection between roots and leaves. This effectively kills the tree, but it leaves the trunk standing until wind and rot combine to bring it down. These standing dead trees are quickly invaded by beetle larvae and other creatures that feast on deadwood. Woodpeckers, of course, feast on these larvae. Woodpeckers also excavate holes in dead trees for nesting and roosting sites. When the woodpeckers are through with them, mammals and other hole-nesting birds use them.
This year at Somme, we have two certain nesting species of woodpeckers: the downy woodpecker and the northern flicker. There are, I think, several pairs of each species. I found one flicker nest in a living oak tree at the southeast corner of the preserve.
I also saw a single redheaded woodpecker on June 8, but I have no evidence of breeding for the species. Redheaded woodpeckers are opportunists. They move into areas where something has killed off large numbers of trees, and they stay until the trees fall and take away their feeding and nesting sites. Somme should be a prime nesting ground for this species, so I will be keeping an eye out for them in the future.
European starlings are among the species that take over those old woodpecker holes, and they are present in numbers at Somme. I found three nests this year-- although I was not looking for them--and whole flocks of young birds were cruising the preserve by the middle of June.
Eastern bluebirds are another user of old woodpecker holes, and I was hoping to find them nesting this year. I had been told that they nested in '89, but I could find no evidence for them this year. I saw two males in March, and other people have told me of sightings since then, but on my visits to the preserve I have neither seen nor heard any bluebirds. It could be that they are nesting somewhere close by and occasionally come to the preserve to feed.
Cooper's hawk, a bird that favors open woodlands, gave me some tantalizing moments this spring. I haven't seen any nests. For that matter I have never seen two birds together. But I have seen one bird, and other people have reported similar sightings. I saw mine along the Milwaukee Road tracks that run north and south through the center of the preserve. The trains can be very helpful for bird counters. They roar through with so much noise and movement that they scare up every bird in the neighborhood, including any lurking Cooper's hawks.
The eastern meadowlarks have been the biggest find of the year so far. I first saw a single male bird way back in March. I had several sightings after that, but always of a single bird. Then on June 12 I finally saw two birds together. There is no visible difference between male and female eastern meadowlarks, but I have seen these two birds together twice more since that first sighting, and one of the birds keeps singing. I'll keep looking for a nest or young.
If the meadowlarks are indeed nesting, they would be the first prairie species to invade the restored prairie on the west side of the preserve and perhaps the first sign of a shift in the bird life created by the restoration efforts.
Overall, the bird life of Somme Woods is still dominated by species whose habitat preferences are usually described with phrases like "brushy edges" or "dense thickets." One of the most common nesting species is the gray catbird, a cousin of the mockingbird. Every patch of dense brush, every woodland edge seems to have its singing male catbird.
The song, while not as wildly inventive and varied as the song of the mockingbird, nonetheless shows the family's fondness for elaborate melody. The nests are hellishly difficult to locate. They are usually hidden deep in the brush. Searching for them--a search that is usually unsuccessful--requires crawling on hands and knees while being stabbed by thorns. Visibility inside these thickets is usually about three feet.
Song sparrows are also brushy-edge specialists, and we also have a few pairs of field sparrows. For a while, I was hearing yellow warblers singing on both sides of the preserve, but the bird on the east side vanished in early June. The nesters are in the line of trees along the fence that marks the western border.
All of these edge birds are frequent victims of parasitic brownheaded cowbirds, and I have been seeing that sinister species in numbers ever since March.
Brightly colored birds are a feature of savanna bird life, and Somme supports cardinals, goldfinches, and indigo buntings. If the bluebirds definitely move in, we will have the whole complement.
The red-winged blackbird is by far the most common bird at Somme. This species used to be confined to marshy areas, but within the past century it has begun to expand into uplands. Somme is saturated with red-wings. You see them everywhere except in the densest and oldest woods.
The most wonderful part of my walks through Somme this spring has been the cicadas. I began to see them in small numbers in late May, and the numbers grew with every visit. They are now everywhere. Every stem of every plant harbors several dull brown nymphs waiting to shed their skins and emerge as winged adults. I usually get to Somme very early in the morning, a time when the adults hang on the trees like ripe fruit. As the morning advances, they take flight. I'm always looking for things in flight, and the constant movement of the cicadas distracts me from the birds. And the noise! A continuous, sourceless keening that comes from everywhere and nowhere. Early visitors to Niagara, people coming on foot through the woods, must have experienced something like this--a constant, distant roar that overwhelmed every other sound.
At Somme, the cicadas actually drown out the traffic noise, the endless rumble that is usually the dominant sound at the preserve. As I walk through the preserve, the noise buoys me, carries me on a tide of energy. This is life, utterly heedless, remorseless, endlessly fecund, endlessly creative, casually destructive. If you haven't been out to experience the cicadas, do it now. You won't have another chance for 17 years.