A thousand-mile journey on two-inch wings

Post by Jen Berlinghof

I’ve spent many days this summer living the “lake life,” from the sandy dunes of the Great Lakes to the cattail-studded coves of inland waters. The waterways found within the Lake County Forest Preserves in northern Illinois have been especially rewarding. Each shoreline has provided unique glimpses of wildlife, including an osprey (Pandion haliaetus) diving full throttle to catch a fish at dawn, and a red fox (Vulpes vulpes) pouncing on prey hidden among the beach grass at dusk.

Also present at every waterway this summer has been the jewel-hued, common green darner dragonfly (Anax junius). These ubiquitous insects effortlessly nab multitudes of mosquitoes on the wing. While the monarch butterfly (Danaus plexippus) reigns in our minds when it comes to insect migrations, recent research reveals the green darner takes a multi-generational, miles-long journey of its own each year.

Common green darner dragonflies (Anax junius) are found in the forest preserves. Stock photo.
Common green darner dragonflies (Anax junius) are found in the forest preserves. Stock photo.

Wildlife migrations are typically monitored using small tracking devices called geolocators. Songbirds and monarchs migrate in such large flocks or swarms that their travels can actually be detected by radar. But green darner dragonflies don’t usually migrate in large groups. Coupled with the fact that the technology to fit an insect weighing as little as a paperclip with a teeny transmitter is only in its infancy, scientists have faced a conundrum of how to track the marvelous migrations of these members of the Odonata order.

A video explaining how researchers revealed green darner migration patterns.

A combo of chemistry and community science provided insight into the last century of dragonfly migrations, as well as environmental impacts for future generations of flyers. Research published in the December 2018 issue of the scientific journal Biology Letters was the first of its kind to use the chemical signatures of dragonfly wing samples to describe the nearly thousand-mile journey these insects undertake on two-inch wings.

A green darner dragonfly nymph. Dragonflies and damselflies of Lake County spend the majority of their lives in this underwater stage of development—anywhere from one to four years, depending on the species. Photo © John C. Abbott & Kendra K. Abbott, Abbott Nature Photography.
A green darner dragonfly nymph. Dragonflies and damselflies of Lake County spend the majority of their lives in this underwater stage of development—anywhere from one to four years, depending on the species. Photo © John C. Abbott & Kendra K. Abbott, Abbott Nature Photography.

A record of the birth waters of every dragonfly is stored chemically in the form of a hydrogen isotope. According to the Department of Energy, isotopes are “members of a family of an element that all have the same number of protons but different numbers of neutrons.” The specific isotopes found in water vary geographically.

As swimming nymphs, dragonflies absorb the isotopes into their bodies and eventually incorporate them into the substance that forms their adult wings. Researchers extracted these chemical trademarks from hundreds of wing samples, pinpointing the general area of North America each insect originated from.

With the home bases for different darners known, migration factors had to be determined. Researchers turned to decades of community science data that suggested these dynamo dragonflies were motivated to move based on temperature and the amount of daylight.

Areas with many dragonflies are represented in red. Areas with no dragonflies at the given point in time are represented in gray. Graphic © Matthew Dodder via Hallworth et al., Biology Letters.

The researchers determined it takes three generations of green darner dragonflies to complete the migration cycle from southern North America to the north, then back again south.

In spring, a first-generation dragonfly nymph emerges from a pond in the American South, sheds its exoskeleton, unfurls its glossy wings and flies 400-500 miles north to lay its eggs before dying. These eggs hatch and complete their metamorphosis by late summer in northern waters.

Some of this second generation will stay put, overwintering as nymphs and waiting out the cold, hunkered down like the rest of us in the Upper Midwest and Northeast. Other members of the second generation have the “travel bug” and hightail it south to lay eggs by late fall along the Gulf and Atlantic Coasts.

This third and final batch of eggs hatches over winter and the adults remain in the warm waters of the South, soaking up the sun. The eggs laid by this third, non-migratory generation will kick off the migration cycle the following spring.

Green darners are named after their resemblance to a darning needle. Photo © Phil Hauck.
Green darners are named after their resemblance to a darning needle. Photo © Phil Hauck.

As summer comes to a close, I’m still striving to live the “lake life.” I walk along the Lake Michigan shoreline at Fort Sheridan in Lake Forest and watch soaring raptors ride thermals overhead as hawk migration gets underway. Closer to the ground, green darner dragonflies zip by on their shimmering wings. Thanks to chemistry and community science, I’m keenly aware of the dual migrations that stratify the skies.

To witness green darners and other wildlife migrating, you might try our Hike Lake County Challenge, now in its 23rd year. Complete seven of the 12 designated trail routes between now and November 30, and you’ll earn a free commemorative shield or zipper pull. Bring your dog along and Fluffy will receive a commemorative dog tag for their collar! See this year’s trails.

Hordes of hummingbirds

Post by Jen Berlinghof

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For me, most days on the job consist of time in my “office” outdoors—a woodland, prairie or wetland in the Lake County Forest Preserves—with my “clients”—students, teachers, and families interested in learning more about local nature. On those rare days spent plunking away at a computer indoors, the photo above is my view. Recently, this view is bustling with activity, as hordes of ruby-throated hummingbirds buzz around the feeders, bulking up for a long flight south.

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Des Plaines River Trail—Route 60 to Route 22

Post by Jen Berlinghof

As the hours of daylight drastically shorten in November, the miles of our hike along the entire Des Plaines River Trail quickly stack up. The trek south along this stretch of the trail from Route 60 to Route 22 was summed up in the stillness of bare branches that were silhouetted against the sky and reflected back from mirrors of water in the surrounding floodplain forest. Continue reading

April Fools’ bird

Post by Jen Berlinghof

It was a windy, but bright, April 1 this year. I was on a trail at Ryerson Woods with a group of volunteers. Most of our heads were focused downward, inspecting the minutiae of a bloodroot bloom. Then, someone shouted, “EAGLES!” I truly thought the next thing shouted would be “APRIL FOOLS’!” but when we snapped our heads skyward, we saw two ivory-headed eagles swooping back and forth above the trees. No joke!

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A snowy spark

Many years ago, while running along the Lake Michigan shoreline late on an evening in January, a feathered ghost appeared on top of a flag pole. It was the first time I had ever seen a snowy owl (Bubo scandiacus) and it stopped me in my tracks. This was the spark on that frozen night that lighted my fire of curiosity about birds. This winter, snowy owls have left their Arctic homes in record numbers, causing one of the largest irruptions (sudden increase) in northern Illinois in decades.

Although it seems natural to correlate the arrival of these boreal birds with the extremely cold, snowy winter northern Illinois is having, experts say the motivator is more likely linked to food. On their Arctic breeding grounds, snowy owls feast under 24-hour sunshine. Their food of choice is lemmings, small mammals with an extremely cyclical population. Bird expert Kenn Kaufman explains in a recent Audubon magazine article, that when the lemming population explodes, like it did last summer in northern Quebec, snowy owls have great breeding success, producing large broods of up to 11 chicks. As these chicks quickly grow into juvenile birds, the competition grows for the now dwindling numbers of lemmings. Thus, the young birds get nudged further and further away to find a meal, resulting in them moving to areas that mimic their treeless tundra home, such as the Lake Michigan shoreline. Continue reading

Heron highrise

This past weekend I had the pleasure of hearing Kenn Kaufman, a naturalist and bird expert, speak at the Smith Nature Symposium. He is somewhat of a “rock star” in the birding world. His novel, Kingbird Highway, chronicles a personal adventure hitchhiking around the country at the age of 16 on a quest to find birds—a story that has reached the status of folklore. Many years later, and surely a much longer “life list,” his keynote address at Ryerson Conservation Area focused on warbler migration: the phenomenon of these teeny tiny birds in every hue of the rainbow that travel thousands of miles across entire continents each spring and fall. He presented complicated doppler maps and in-depth scientific research on these migratory dynamos, but by the end of the discussion the focus had shifted to something more simple: the children from his young birders club.

guide-bookLate that evening, as I settled down with one of his many guide books, Field Guide to Advanced Birding, I was struck by this same theme of simplicity. Kaufman urges folks to slow down and focus not on looking for the birds, but instead to spend time looking at the birds. He stresses getting to know the common birds of an area very well. By doing so, we are well on our way to knowing when a rare bird may enter the scene. This concept brought to mind one of the best places to take a long look at one common bird of Lake County, Illinois: a great blue heron rookery.

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Where do insects go in the winter?

Post by Allison

Earlier this week, my husband came in from the yard with a mosquito on his forehead. Had it been summer, that little tag-along would never have made it so far—but not in December. In the colder months, critters that are commonplace during the Midwestern summer are often the farthest things from our minds. It always amazes me when the weather has been cold for an extended period, then, at the first sign of warmth, insects seem to magically reappear. Where have they been hiding? How did they survive the frigid air that makes me shiver in my sweater when I’m outdoors longer than a few minutes?

Where do insects go in the winter?

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Warbler fever

Birding fever hit a high this past weekend in natural areas throughout northern Illinois. Birders flocked in throngs with binoculars strung on their necks like potential Olympic medals and a hope of spotting some of the most coveted migratory birds— wood-warblers. Members of the family Parulidae, wood-warblers are the colorful jewels of migration from the sapphire blue of a cerulean warbler (Setophaga cerulea) to the amber orange of a Blackburnian warbler (Setophaga fusca). Yet, as these birds flit about in the treetops, no color is as visually striking as the lemony-yellow citrine that adorns so many warblers as they pass through our area on a flyway. Once these impish birds reach their destinations (as far as northern Canada for some species) and breed, they will molt their flamboyant plumage and become far less conspicuous, which is why seeing them in the spring is considered such a prize for birders.  Continue reading

Glimpses from the car window, bootprints on the trail

Like most of you reading this, my life is busy. Even though I work outdoors in the forest preserves, not all of my nature experiences occur there. Many days I have to take the glimpses of nature where I can get them. On my drive home from work last week, glancing at the “not-so-glamorous” retention pond next to the tollway, I spotted my first hooded merganser of the year. I knew the gang was back, although some of them not for long. This “gang” I’m referring to is the group of migratory waterfowl that show up here in the early spring during migration en route to their final destinations further north. With names like horned grebe, American wigeon, northern shoveler, and gadwall (just a few of the species seen in the past few days at Independence Grove Forest Preserve, here is the complete list), who wouldn’t want to meet this cast of characters?

This time of year is the perfect opportunity to take a peek at some fascinating birds close to home. Continue reading