American Robin Dossier

by Carl Strang

 

Today’s post is another in my series of species dossiers. It begins with the summary paragraph written when I established the dossier in late 1986 or early 1987. I have edited out some less informative entries.

 

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American Robin. Familiar bird of natural and artificial savannas. Primarily a summer resident, although small numbers remain in northern IN and IL around fruit-rich areas as long as winter weather is not too severe. Waves of migrants seen each spring and fall. Nest typically on branches of broadleaf trees, or in shrubs. Nest of grasses and mud, with deep inner cup. Sometimes grasses dipped in mud before delivery to nest. Eggs deep sky-blue. Young may get out of nest a short distance a couple of days before fledging, but after early-morning departure from nest they tend to travel some distance and do not return. Young scattered, tended individually by parents, who swoop and may peck at people or mammals which approach the young. Fledglings have dark spots on breast. Worms and insects hunted on ground in summer; fruit the winter food. Mulberries eaten by both adults and young in early summer. Winter berries include buckthorn, mountain ash. Song dominates habitat in early morning and dusk. A musical series of phrases, each composed of 2-3 clear, slurred whistling notes sung from mid to high perches in trees, on aerials, etc. Alarm call “cheet’-der-der-der-der.” Occasional battles, presumably territorial, take place. Striking white spots on tips of tail feathers may be “follow-me” signals. Preyed upon by cats, on occasion. When hunting worms, run 2-20 feet over the ground, stop, then may move a short distance, lean down with side of head turned toward Earth, then possibly reach down and pull up worm with beak.

26AP80. Pennsylvania. Robins, when startled into flight across the path of an approaching car, appear to use body-twisting and turning tactics more appropriate to flight from a hawk.

14JE87. Young-of-year eating mulberries at Culver Fish Hatchery.

9SE87. Large flock in Willowbrook Back 40. One ate grapes.

16SE87. In the evening, within a half-hour before sunset, robins were migrating south over Willowbrook. They flew just above treetop level, in flocks of 3-30, occasionally perching to rest for a time in the treetops, then moving on. The birds occasionally called to one another in flight, alternately flapping in short bursts, and gliding.

29AP88. A robin on a nest at Pratts Wayne Woods Forest Preserve, 6 feet up in crotch of a 15-foot, 3″dbh fencerow box elder.

7AU88. Young robin, apparently independent but still with spots, eating black cherries in Willowbrook Back 40.

30AU88. Lots in Back 40, mostly on ground but 1 in black cherry going after fruit.

5OC88. Robins eating grapes, Back 40.

6OC88. Robins eating gray dogwood fruits, Back 40.

12OC88. Robins eating honeysuckle fruits, Back 40.

17JE89. A broad-wing calling repeatedly, in north end of Maple Grove Forest Preserve. Robins definitely disturbed, with nervous dee-dee-dee’s every 20 seconds or so.

28AU89. Robins eating gray dogwood fruit, Back 40.

21OC89. Robins eating buckthorn berries, West DuPage Woods Forest Preserve.

3JA90. A robin singing very softly at Herrick Lake Forest Preserve. Temperature ~40F, sun.

 

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14JA90. A large robin flock, scattered in woods on ground, moving as they do when hunting worms. Ground frozen. Saw occasional reaches to turn over a leaf, but no feeding.

7AP90. Robins in forest at Winfield Mounds Forest Preserve, throwing leaves with beaks to find food.

2JE90. Culver. A robin foraging on lawn (20 feet from nearest shrub) singing, 7:30am.

14SE90. Willowbrook, robin ate a couple small grapes, swallowing them whole.

JA99. Robins present on Willowbrook preserve all winter. Heavily fruiting asiatic bittersweet (Celastrus vine) a particular attraction.

6FE99. At Morton Arboretum, in an area thick with honeysuckle beneath a mesic forest, many robins feeding on the ground, vigorously throwing leaves aside and eating very small things too quickly to identify. I dug, found a mix of insects and fruit-like items.

9SE99. 2 robins eating buckthorn berries at Willowbrook.

13OC99. Robin occasionally singing at Willowbrook.

8FE00. Robin eating buckthorn berries at Willowbrook. They are fewer and more intermittent than last winter, 1 or 2 at most at any time.

13AP00. Willowbrook. One robin chasing another in the savanna. Could robins have nested in prairie savannas in years when fire burned off the tall plants beneath the trees? They might have fledged an early brood before the new plants got too tall for them.

16AP00. Willowbrook. A robin carrying nesting material.

1JE00. Arboretum. Along the Joy Path, a robin was perched in the lower branches of a maple, well concealed from above by leaves, sitting absolutely still and barely opening its beak at intervals to give a high-pitched note, somewhat waxwing-like but louder, better defined, that was difficult to locate.

15JE00. Arboretum. Near Parking Lot 7, when I arrived around 8am, 3 robins were giving the high‑pitched thin call repeatedly, and the forest otherwise was relatively quiet. After 10 minutes, a Cooper’s hawk started calling nearby, then flew out away from the forest edge until an eastern kingbird started to chase it. It immediately turned around and flew back the way it had come, and kept going. The robins then were quiet.

16JE00. Willowbrook. In the afternoon, a Cooper’s hawk perched near the west edge of the prairie, drawing alarm calls from a robin (the hawk‑whistle warning call) and a cardinal, and a chorus of 7 loudly mobbing jays.

5JL00. Willowbrook. Many robins, adult and first‑year, on the preserve today. A young one, and also a red‑bellied woodpecker, sally‑foraging for insects, possibly flying ants, from the top of a tall dead tree near the stream. (One passing insect was observed for a few seconds before the robin flew out and caught it).

11MR01. A robin singing loudly, Timber Ridge Forest Preserve.

28JL01. A newly on-its-own robin chased a cicada through the air, the insect giving its predator-discouraging call, but broke off the chase and flew back the way it came. The robin was never close to the cicada during the part of the chase I saw.

13MR02. First morning of robin (or any) dawn chorus at my house.

Singing Insects

by Carl Strang

 

As summer proceeds, the outdoor airwaves that were dominated by bird songs in the spring become less and less so. In their place we hear buzzes, whirrs, ticks, clicks and chirps: the songs of insects. I long had been interested in finding out more about the different kinds of insects that make these sounds, but was frustrated by what I was finding in print. Then some great web sites began to come on line with sound recordings, new CDs and books with enclosed recordings became available, and so my top inquiry interest in recent years has been singing insects.

 

Black-horned or Forbes's tree cricket, wings lifted to sing

Black-horned or Forbes's tree cricket, wings lifted to sing

 

 

 

The first source I found was the cicada website maintained by the University of Michigan. Its focus is Michigan cicadas, but its recordings are relevant to northeast Illinois as well. I found that the cicada songs of late summer are variable because they are produced by different species, and I began to note which ones I was hearing.

 

A couple years later I came across the Singing Insects of North America website, managed by the University of Florida, which attempts to cover all North American species. Its coverage of crickets and katydids is especially good, and I went through it listing species I might expect to find in my area. It has recordings of almost all of them.

 

Rattler Roundwing Katydid

Rattler roundwing katydid

 

 

 

Published resources I have found useful are the CD Songs of Crickets and Katydids of the Mid-Atlantic States by Steve Rannels, Wil Hershberger and Joseph Dillon; and Field Guide to Grasshoppers, Katydids, and Crickets of the United States by John L. Capinera, Ralph D. Scott, and Thomas J. Walker (it doesn’t include sound recordings, but has good information). One of its co-authors, Tom Walker, directs the Singing Insects of North America website. An excellent recent book which includes an outstanding CD is The Songs of Insects by Lang Elliott and Wil Hershberger, who also have a website.

 

Striped ground cricket

Striped ground cricket

 

 

 

Almost all of the singing insects are cicadas, crickets and katydids. A small number of grasshoppers also produce songs but these are few in Illinois, and seldom are among the sounds we notice in the field. We have more than 50 species, and I continue to sort out new ones each year.

 

I have already shared my most complete study, of periodical cicadas, which emerged locally in 2007. In the future I will feature other aspects of what I have been discovering.

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.

 

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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.

 

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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.

Off-year Emergences

by Carl Strang

 

This is the third entry in a series describing the periodical cicada emergence of 2007 in northeast Illinois. In the introductory entry I referred to an off-year emergence in 1969, four years before the main 1973 arrival. Henry Dybas of the Field Museum compiled reports from DuPage and adjacent counties that indicated large numbers of the insects appeared in many communities in 1969. In general only a portion of the local cicada populations came out early, and he expected them to be consumed by predators before they could produce enough eggs to result in an ongoing off-year splinter population (or, to use a term coined by cicada specialist Gene Kritsky, “shadow brood”).

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Newspaper accounts, and observations by Illinois entomologist Phil Nixon, demonstrate that good numbers of cicadas emerged in the subsequent off years of 1986 and 1973. There apparently is not enough documentation of reproduction to confirm that this is a continuing shadow brood rather than fresh subgroups of cicadas emerging 13 years after the main emergences each time. This is such a rare event across the range of periodical cicadas that it seems more likely that the original 1969 shadow brood has maintained itself, reverting to a 17-year spacing and reproducing enough to maintain itself, at least so far. But we cannot entirely rule out the possibility that there is something different about parts of the Chicago area, or about the cicadas that live here, that prompts unusual percentages of early emergences each generation.

 

magicicada-pale-6b

 

We do not know what prompted the shortened lifespan of these insects. Underground competition is one possibility. Something strange about the rhythm of flow in the tree sap annual cycle between 1956 and 1969 might have thrown their count off. The mechanism is not entirely mysterious, however. Each northern species of 17-year periodical cicada has a counterpart 13-year species in the South. Researchers Jo Ann White and Monte Lloyd found that there is a simple developmental difference between the species in each pair. The northern ones go into a 4-year dormancy early in their development, then snap out of it and resume growth on the steady schedule. Something made some of our Chicago-area cicadas act like southerners, skipping the dormancy.

 

magicicada-pale-11b

 

So far all of this is old news, and except for the fact that I observed some of the 1973 cicadas myself, what is my rationale for including it in my inquiry blog? The reason is a mysterious hole in the distribution of cicadas I observed in 2007. Two adjacent DuPage County communities, Wood Dale and Addison, had essentially no periodical cicadas last year. This was unexpected, as they were on Dybas’ list of communities with cicadas in 1969, and they are adjacent to cicada rich Bensenville. They should have contributed to the third lobe of the main cicada emergence along the northernmost of the three commuter railways mentioned in my introductory entry on this subject.

 

I have interviewed a number of people who live or work in that area, and looked at old newspapers. There were plenty of cicadas in both towns in 2003. I have come to the tentative conclusion that in their area it wasn’t just a portion of the local population that emerged in 1969 but rather the bulk of it. So few were left for the main emergence that Dybas’ prediction of predator elimination ironically may have come true, wiping out that correct-year emergence group, so that essentially only the shadow brood remains in Wood Dale and Addison two generations later.

 

If I am still around in 2020, I intend to repeat my mapping of periodical cicadas in the county, this time to document what appears to be an ongoing local shadow brood of the insects.

 

Tomorrow: UFO’s

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.

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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.

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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…

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