Several times each summer Doug Taron walks a precisely plotted route through Bluff Springs Fen and counts butterflies. He notes his starting and finishing time and records each sighting along the way. His tally sheet is divided into five columns so he can separate the insects seen under the shade of the old burr oaks in the savanna from those encountered on the gravel hill prairie, in the fen itself, in degraded portions of the preserve, or in areas that are being restored.
This is his 11th season as a butterfly monitor at the fen, and the records he is accumulating are part of a growing body of solid information about the state of our local lepidopterans. The information is being gathered by some of the several thousand people in northeastern Illinois who are part of the Nature Conservancy's volunteer stewardship network.
The butterfly monitors are trained to recognize free-flying butterflies on sight, though they carry nets just in case. They carry out a standard protocol that allows statistical comparisons between sites and between years. When the program began in 1987 only about ten sites were covered. But more volunteers have signed up, and now about 40 sites are monitored regularly.
Bluff Springs Fen, an Illinois Nature Preserve, is one of the most beautiful places in northeastern Illinois. It lies on the eastern outskirts of Elgin, just far enough east to be in Cook rather than Kane County, and encompasses 91 acres. It is owned by the Metropolitan Water Reclamation District. It is quite hilly, and the hills are kames. Kames form under glaciers from materials carried by meltwater. They are generally made of gravel, which makes them very attractive to companies that make concrete. Most of this region's kames have been mined down to ground level.
Precipitation flows easily into the gravel at the top of the kame. It percolates down through the gravel, emerging in seeps and springs on the slope or at the foot of the kame. The gravel is mostly limestone, so the water picks up large amounts of calcium and other minerals in its travels. Where it emerges, specialized plants that thrive in the extremely alkaline water form communities called fens. Where there are specialized plants there are often specialized animals as well.
The fen at Bluff Springs sits in a valley surrounded by kames. Gravel hill prairies cover some of the kames, but enough of the hilltops are covered with burr oak savanna to shield the preserve from the outside world. Once in the preserve, you feel like you are in a wilderness with no sight or sound of the outside world to destroy that illusion.
Last Saturday I followed Taron around on his route and absorbed as much butterfly information as I could. It was a beautiful summer day: hot but not brutal, and with very little wind to interfere with the flight of butterflies. The diverse natural communities at the preserve gave us a rich floral display. The yellow of cup plant, prairie dock, compass plant, and black-eyed Susan; the pink of blazing star; the blue of wild bergamot; and the white of flowering spurge.
I have been doing surveys of nesting birds for several years, and I am used to getting up in the predawn darkness so I can arrive at my survey site by sunrise. Butterflies keep more sensible hours than birds, so Taron and I started the route at ten o'clock.
We weren't 20 feet down the path when I saw two cabbage butterflies fluttering off to the right. I pointed them out to Taron and got my first lesson in staying with the protocol. His data were based on one pair of eyes doing the looking. If I added my observations he would lose the consistency necessary to the program. So I kept quiet.
Our next butterfly was a monarch, the first of many, and then a banded hairstreak fluttering up from a burr oak limb after Taron smacked the limb with his net. "We probably miss most of these," he told me. "They sit on the limbs, but most of them are up in the crown where we can't see them. But we can get relative abundance."
Banded hairstreak caterpillars emerge from last year's eggs in spring. They may be among the attractions that lure so many migrating birds into oak trees.
Wood nymphs are out in force. These medium-size brown butterflies range from the shady spots under the oaks to the flowers of the tall-grass prairies. Taron finds a red-spotted purple, a butterfly I have never seen before, checking out cherry leaves before depositing eggs. The red-spotted purple has a wingspan of three inches. The red spots line the edges of the undersides of the wings. From above, the insect is purple, deep blue, and black.
Female butterflies use chemical sensors in their feet to find suitable plants for their eggs. Caterpillars specialize to varying degrees. Some can feed on whole families of plants, or on select plants from various families. Some are confined to a single genus or even a single species.
Taron talks of how a butterfly monitor has to constantly change his focus, quickly shifting from near to far and high to low to avoid missing any insects. Birders do that sort of thing all the time, so I am familiar with the drill. But one major difference emerges between birding and butterflying. I know many experienced birders who can barely tell a burr oak from a loblolly pine. Butterfly study is more demanding. The lives of these insects are much more bound up with specific plants: the leaves the larvae need for food, the flowers the adults need for nectar. A good butterfly monitor has to know at least a little botany.
Our route takes us right through the fen past shrubby cinquefoil, a rare and specialized plant now in golden flower. Viceroys are mixed with monarchs out in the wetlands. The two butterflies are almost identical, providing an excellent example of protective mimicry. Monarch caterpillars eat milkweed, a diet that makes both them and the adults taste terrible. A bird that has never seen one before will eat one, but never two. The viceroy's mimicry protects it from predators. Taron points out the black streak on each hind wing that makes it possible to tell one from the other. Later we see a viceroy female laying eggs on a willow, the preferred food plant of the species.
The last 200 yards or so of the route are off the trail through very difficult terrain. Dense growths of brambles and thistles tend to distract your attention from the ground where fallen logs are hidden among the vegetation ready to trip the unwary. Sinkholes are another hazard. Step in one of those, and you might be looking at knee surgery.
Our results for the day: 140 individuals of 16 species. Taron tells me that we are in a lull between the midsummer species and the late-summer species. Of course birders and fishermen have their own versions of that story--you should have been here last week!
With the counting done, we sat in the shade, and Taron talked about what the monitoring is teaching us. The first lesson is about the importance of long-term studies. "There are quick fluctuations in populations that really don't mean anything. This is my 11th season here, and I am beginning to see trends."
The trends are heartening so far. Three species: the eyed brown, the Baltimore checkerspot, and the black-dash skipper are showing significant increases in population. This is especially important because two of these insects, the checkerspot and the skipper, have been identified as "remnant dependent." That is, they do not occur outside of special places like Bluff Springs Fen, places where the native vegetation of the region still dominates the landscape.
The fen has been under an active fire regime for several years, but no species has shown any decline. Thus far, all have been either helped or unaffected by the prescribed burning.
Taron is looking forward to the data that will become available during the next few years as the sites added to the program in 1991 begin to reveal long-term trends on many more sites. His interest in butterflies goes back to childhood, when he was a collector with specimens pinned to boards. "That was the only route open to someone with an interest in butterflies. The monitoring has created a completely new way. You meet them on their own terms."
A few weeks ago Taron began a new job, one that will let him help others experience the joy of meeting butterflies on their own terms. After years as a researcher studying the genetic aberrations associated with cancer and birth defects, he has joined the Chicago Academy of Sciences as an exhibit coordinator. One of his major responsibilities will be to create and oversee a living exhibit of butterflies from this region.