DuPage Robust Coneheads

by Carl Strang

Last year, while conducting an evening survey drive to map fall field cricket distributions in my home county of DuPage in Illinois, I was passing through Springbrook Prairie Forest Preserve when I thought I heard a couple robust coneheads singing.

Male robust conehead in singing posture, Newton County, Indiana

Male robust conehead in singing posture, Newton County, Indiana

This was surprising, and I wasn’t able to follow up in 2012, but it was on this year’s research checklist, and on Monday evening I heard them again in the same location. I found a place to park, and to make a long story short was able to confirm my suspicion (a later sonograph analysis of the recording I made will determine whether this was a robust conehead or, less likely given the loudness of the song, a false robust conehead).

This discovery was surprising because in general I have been finding them, as researchers in past decades also have noted, mainly in areas with sandy soils.  No such soils exist outside children’s playgrounds in DuPage. On the other hand, no lesser a light than Richard Alexander listed DuPage County as a place where he had found the species a few decades ago. This is not a simple matter of latitude, as robust coneheads are abundant in sandy Lake County, Illinois, to the north. This species joins the tinkling ground cricket and spring trig as species that I have found in the county, but only in extremely small numbers in one or two places. DuPage County, out of all the 22 counties in my regional survey, is the one I have surveyed most thoroughly, and for nearly 8 full seasons. These few locally rare species are indicators that there probably will be holes in my distributional records for all counties, and so these will need to be judged accordingly. I will need to continue searching for new sites through the seasons and years, as long as I am able to do so.

African Bird

by Carl Strang

 

I’m not a huge TV watcher, but “Survivor” is one of my guilty pleasures. The current series, taking place in Africa, occasionally shows a passing shot of a species of bird I have seen a number of times despite never having visited that continent. It’s also a species which nests in northeast Illinois. I’m talking about the osprey.

 

Osprey nest, Maryland Eastern Shore

Osprey nest, Maryland Eastern Shore

 

 

Ospreys occur all around the world. I saw them in Australia. Though there are no recent known nests in DuPage County, for the past two seasons there has been one a stone’s throw from the county’s northwest corner. I should say “baseball’s throw,” because this nest is built on one of the light poles in a complex of ball diamonds. It’s tempting to say the birds must be baseball fans.

 

For one species (and there is only one) to have become so cosmopolitan is testimony to the success of its complex of adaptations. Freshwater fish that stay close enough to the surface to be susceptible to a plunge-and-grasp are found on all the warm continents. Ospreys’ feet are wonders. The long curved talons are supplemented by hard sharp protruding scales on the undersides of the toes that grip the slippery prey.

 

Osprey carries fish head forward

Osprey carries fish head forward

 

 

My best opportunity to watch ospreys in action came during my sea kayak circumnavigation of Isle Royale a few years ago. I camped a couple days at a site called Hay Bay, which is accessible only by boat or bushwacking. There I had an excellent opportunity to watch ospreys, cormorants and gulls as they hunted for the abundant lake herring. The ospreys plummeted from spectacular heights, and when it was calm I could hear their collisions with the water from most of a mile away. Often they rose with fish that were at least a third of their own length.

 

Recent nesting success of ospreys in northeast Illinois bodes well for their return as a more familiar part of our fauna.

Periodical Cicada Behavior

by Carl Strang

 

This post will conclude my account of periodical cicadas in DuPage County, Illinois, during the 2007 emergence. I had read as much as I could find, from the scientific and popular literature, regarding these insects, but there is no substitute for direct experience. It’s one thing to read that the choruses of singing males are loud, it’s quite another to find that you have to wear ear plugs during lunch time excursions because of concern that hearing damage might result from walking under chorus trees.

 

magicicada-feeding-closeup-b

 

With that caveat, of course the literature described things well enough, for the most part. There are no absolutes, though, when you are talking about millions of individuals of any animal. Yes, they mainly came out at night. But some came out during the day, especially on rainy days. There were appalling numbers that became stuck and did not complete their emergence. These died half out of their nymphal skins, or sometimes simply had deformed wings and could not fly. I saw crinkle-winged females laying eggs, though. With numbers so great, finding a mate was easy, and so there appeared to be less selection against developmental deformities than you might expect.

 

Crinkle-winged female laying eggs

Crinkle-winged female laying eggs

 

 

 

 

I went out a few nights to observe emergence. On one cool night I heard rustling in the leaves on the ground, but nothing happened, and things quieted down. On a warmer night, the rustling proceeded to hordes of nymphs climbing plants to complete development to their final adult form.

 

magicicada-night-emergence-2b

 

The cicadas usually were quiet through the night and into the next morning, most flying into the tree canopies by mid-day following their emergence. I’m really just sketching here, there is so much that has to be observed first hand. Let me jump ahead to the most unexpected behavior of all.

 

The cicadas had been out for a couple weeks, perhaps, and had proved to be conservative in their movements. I found that, at the edges of main emergence areas, I could find choruses of males singing 100-200 meters farther out. They flew around some, but did not fly into the open.

 

Then suddenly, over a period of three days or so, all of this changed radically. Cicadas were flying out into the open, across wide highway corridors for example. After that brief period, small choruses of males were singing all over the county, even in areas where there had been no emergence. I found females in some of those places, too.

 

Emergence holes

Emergence holes

 

 

 

 

This was unexpected, and exciting. I didn’t recall seeing anything about this in the literature. So, what does it mean? Is this something that always happens? If so, it doesn’t mean much in terms of cicada populations. These adventurers will have no long term impact if they leave no descendents. But what if this was a unique event, brought about by some fortunate confluence of environmental conditions with a population that had reached a cusp from which large-scale expansion suddenly was possible? If the latter is true, there will be a radical change between the 2007 map and what will be observed in 2024. But, sigh, all we can do now is wait. The next generation is under ground, now, entering its 4-year dormancy at this point, continuing its slow count of years until the time is right for the next round of inquiries into the mysteries of the periodical cicada emergence in northeastern Illinois.

Where the Periodical Cicadas Were

by Carl Strang

The questions that inspire an inquiry are not always profound. Sometimes you just want to discover what is out there. Sometimes you want to experience something wonderful, and your question is: what will it be like? My 2007 study of periodical cicadas in DuPage County started on this kind of level. Sure, there was a little more to it than that. There is a considerable literature built up on these insects, and many questions remain unresolved. For instance, Henry Dybas, a former scientist with Chicago’s Field Museum, documented a strange off-year emergence of periodical cicadas in the Chicago area, 4 years ahead of their anticipated 17-year appearance, in 1969. Such events since have been observed elsewhere, but no one has explained why. He predicted they would have no descendents, because they all would be consumed by predators before they could reproduce. It appears he was wrong, but that’s a topic for another time. For now, I want to focus on the fact that the DuPage County communities in his 1969 list were all in the eastern half of the county. That was the closest thing we had to a geography of periodical cicadas in DuPage before the 2007 emergence. No one had ever mapped them. So, my first goal was to produce such a map and see where it led.

 magicicada-wingstem-2b2

In the meantime, I would be witnessing one of the wonders of the wild world. Dybas and his research partner, Monte Lloyd, found that periodical cicadas in northeastern Illinois come out in amazing numbers, in places at a rate of 1.5 million per acre. The males congregate in trees to sing in choruses which guide the females to them. Here in the north they emerge at 17-year intervals, with very few typically coming out in other years (I call the latter oops! cicadas). They spend only a few weeks above the ground, otherwise living as subterranean nymphs sucking sap from tree roots.

 

It will take several installments of this blog to spin out this story. For now I want to focus on where the cicadas emerged in large numbers in 2007. I drove and bicycled all around the county seeking cicadas in the first days after they began coming out in good numbers. I concentrated on mapping the edges of high density areas, while documenting areas where there were smaller numbers of them and spot checking the interiors of major emergence zones. The results were pretty clear cut, as my working map illustrates. Dybas’ list of towns for the off year emergence matched fairly well the cicada distribution in 2007, with the concentration zones generally in the eastern half of DuPage County.

 magicicada-map-b-rr1

But what caught my attention was the 2-lobed shape of the main emergence area. Those lobes were not randomly placed: they centered on the two major commuter rail lines that pass through the county (highlighted in blue). Furthermore, the little isolated island of cicadas in the northeastern corner of the county is on the third commuter line. The large emergence area in the southeastern corner of the county includes Waterfall Glen and adjacent forest preserves, comprising a large forested area along the Des Plaines River that is unsurprising as a cicada area. So, before you read further, here is a question for you to ponder: what do periodical cicadas have to do with railways? A related second question is, why didn’t the cicada emergence extend all the way to the western border of the county?

 

Here is part of my answer. Cicadas don’t need to commute. If you drive around the county, visiting its towns, you can observe that the towns along those railways have the greatest concentrations of old trees. Those towns, especially the ones closer to Chicago in eastern DuPage, grew earliest, supported by the rail access. People piled into those communities early and planted trees around their homes. The urban forests became prime periodical cicada habitat. The railways happened to pass close to forest islands in the prairie where periodical cicadas lived, and those populations seeded the growing urban forests. Communities between the rail lines lagged behind in their growth and their tree planting, and the periodical cicadas, with 17 years between generations and a limited ability to spread in each generation, have not had time to spread into all forested areas, yet.

 

So that first, basic question of where the cicadas would emerge led to this answer. But there are more questions to address. I think I have answers to some of them, and will share that information in future installments. For now, in the spirit of inquiry, here are some of those questions:

  • Why were there nearly no cicadas in well forested areas in the western half of the county?
  • What became of the cicadas that emerged in 1969? Did they leave descendents to emerge, again four years ahead of main emergences in 1976 and 2003?
  • There are three different species of 17-year cicadas. Were they all present in DuPage? How did their distributions fit the general pattern?
  • Did behavior of cicadas match expectations from the scientific literature? Were there any surprises?
  • What about the distribution of cicadas in areas surrounding DuPage County?
  • What can we expect in future emergences?

 

To be continued…

Introduction

by Carl Strang

 

In this blog I will focus on natural history investigations in northeastern Illinois (especially DuPage County) and the surrounding region. My greatest attention will be given to insects (especially singing insects, damselflies and dragonflies), birds, mammals and geology. By “investigations” I mean a broad range of studies, from general or anecdotal observations to more focused scientific studies. The purpose is not only to share information but also to encourage others to go from general nature appreciation to more focused attention with a scientific approach. In particular I hope that this will encourage children and teachers to learn about science from the inside by conducting their own inquiries in the outdoors. I will make occasional reference to the scientific literature and to technical points and theory, but I intend to do so in a manner readily digestible (and, I hope, enjoyable) for those who lack a formal background but have an interest in natural history.

 

Though I work as a naturalist for a county park system, this is a personal blog and does not in any way represent my employer. Inevitably, however, much of what I report will be observations within the properties of the Forest Preserve District of DuPage County. I also may use this space from time to time to promote opportunities related to its subject matter within the District.

 

My background is a Ph.D. in wildlife ecology, in which the thesis work was a study of glaucous gulls in western Alaska in the early 1970’s. After a 5-year stint of college teaching during which I studied wood and eastern box turtles, I retread myself as an interpretive naturalist. Though I no longer need to publish (and don’t have funds to pay journals’ page fees!), my interest in doing science remains. Since moving to Illinois I have been studying leaf eating insects in the forest understory (especially leaf miners of sugar/black maples, and interactions between an ermine moth and a trailing woody plant), and more recently singing insects (general survey work has not been done in Illinois since the 1930’s; also I did a focused study of periodical cicadas during their 2007 emergence). I have been a dragonfly monitor since the inception of that program in the Chicago Wilderness consortium. Smaller studies have indulged my curiosity about the social structure and movement patterns of whitetail deer; the route followed by the local lobe of the most recent continental glacier; and I soon will attempt an inventory of Canada goose winter flock roosting and foraging geography within the county. In addition I make broader observations that allow me to follow the natural history of the properties where I spend the most time (my home neighborhood, and the preserve where my office is located). This is science in the old fashioned sense of satisfying general curiosity, which academics no longer have the luxury of indulging. Their pressure to focus on narrow theoretical or applied subjects has its costs, and I hope that this blog will compensate in a small way.

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