by Carl Strang
Not long ago I mentioned that I have begun listening for songs of the swamp cicada, Tibicen chloromera, in DuPage County. Since then I have heard some songs that seemed close, but none that were completely convincing. That changed on Wednesday morning, when I heard unmistakable songs from several individuals of this species at Springbrook Prairie Forest Preserve, in southwest Naperville. The habitat and song perches were just as the literature would lead one to expect: the cicadas were singing from small bur oak trees in a mesic prairie adjacent to a stream. Specifically they were in the Springbrook “remeander” project area.
The photo, taken in 2007, shows the stream shortly after it was converted from a ruler-straight ditch to a stable channel shape with bends, or meanders. Alongside were planted the small bur oaks and a variety of prairie forbs. There is no historical evidence for a natural meandering stream at the site, so it is likely that a sheet-flowing swale, rather than a defined, meandering streambed, preceded the straight ditch. The meanders have the effect of reducing the stream’s steepness, slowing it down so erosion is minimized. Aided by the resulting diverse array of pools and riffles, the stream can support a greater diversity of life. The project rightly has earned several awards for the Forest Preserve District of DuPage County. Two Naperville high schools send Advanced Placement Environmental Science classes to collect data from the project each year, and I was there on Wednesday in connection with that educational dimension.
The cicadas did not sing for a very long time. I wonder if their being closer to the edge of the species’ range explains the more limited habitat variety, song perch choice and singing period I seem to be finding in DuPage County, compared to chloromera I have been observing in the more southern Culver, Indiana, area I referenced in the earlier post. Such thoughts will inform my continued search for swamp cicadas in DuPage.