Friday, June 24, 2016

Cicadas!

I could hear murmured gasps of surprise and appreciation as the Wisconsin Master Naturalist Volunteer students stepped out of the car caravan and into the Moquah Barrens. Rolling hills carpeted in grass and punctuated by pines stretched as far as the eye could see. Vistas aren’t common in Wisconsin. Our Northwoods landscape is dominated by dense trees. In contrast, the deep sand deposits left by glaciers on the Bayfield Peninsula provide the substrate for a grassland ecosystem reminiscent of the Serengeti.

Matt Bushman, the botanist on the Superior National Forest, gathered the group around to start talking about plants. As he held up sand cherry, smooth aster, and Pennsylvania sedge, the heavy clouds parted and a tentative sunshine brightened across the savannah. As the light strengthened, a high buzzing became noticeable and then intensified. The crescendo was so perfectly synchronized that it seemed as if the sunshine itself came with sound effects.

From behind my head I heard one particularly loud buzz. Not really expecting to see the source, I nonetheless peeked over my shoulder. To my surprise, I easily spotted the noisy cicada as it perched in a small jack pine tree. 


Cicadas are true bugs with wide-set eyes, short antennae, and big, clear front wings. They make noise not by rubbing together hind leg and forewing as in grasshoppers and crickets, but by rapidly vibrating a portion of their exoskeleton. The drum-like tymbals are a pair of corrugated membranes on the sides of the cicada’s abdomen. As the tymbals vibrate, the male cicada’s hollow abdomen acts as a resonance chamber and amplifies the sound. 

Before long the sun disappeared above a passing downpour. We jumped into vehicles and bounced along a sandy road to our next site. The rain abated quickly as we gathered to admire a fresh burn. Just this spring the Forest Service had ignited a prescribed fire in this management block. The ground was still inky black with soot and charcoal, but already the bracken ferns had erupted in a neon green ruff across the hills. 

Sunlight and buzzing filled the air. The class hoofed it uphill, picking their way through the shin-high forest of bracken. Something caught my eye against the black ground. A large, adult cicada crouched silently. Its huge, clear wings folded neatly over its dark back like a clear plastic poncho. Through the membranes I could see delicate orange bands on its abdomen, orange legs, and more orange markings behind its head. Wide-set, dark eyes fronted its alien head. 


Nearby, still clinging to a charred stick, I found an empty shell. This wasn’t the body of a dead cicada, rather it was the discarded exoskeleton of a young cicada who had emerged and flown off as an adult. The exuviae, as scientists call them, were everywhere: tumbled on the ground, hooked to vegetation, blown into small drifts against the base of stumps. 

As I looked down I began to see their tunnels, too—inky black, round holes as if we’d all just poked our fingers in the soil. 

Cicadas have a fascinating life cycle. After seeking out a loud male and mating, the female cicada slices open a twig and lays her eggs. Upon hatching, the nymphs drop to the ground and use their strong front legs to burrow in. The nymphs will spend most of their lives about eight feet down, sucking up the sap of plants.

The number of years that a cicada nymph spends underground varies by species. Most types reach adulthood in two to five years. The most famous cicadas, though, are the 13-year and 17-year periodical cicadas of eastern North America. They emerge all at once in tremendous numbers. Their genus, appropriately, is Magicicada.

Magic indeed. Eyes on the ground, we soon found our own enchanted fairy. Perched on the empty exuviae—which was still hooked to a stick by tiny claws—sat a cross between a pixie and an alien. Huge, clear wings were threaded with glowing white veins. The plump, seafoam green body was etched with pale yellow and orange highlights. Staring straight at us were a pair of false eyes, with the vertical pupils of a cat.


Once a cicada nymph crawls out of its hole, it climbs partway up a nearby plant, splits its exoskeleton between the shoulders, back-dives free, and then slowly hardens off and darkens in color. With shouts of excitement, we discovered a cicada in mid-back dive, its wings still folded like baby leaves. 


Magic as these were, they weren’t the 17-year cicadas. Those adults have red-orange eyes. A quick internet search brought up the tentative identification of Okanagana balli, the Short-Grass Prairie Cicada. (A species with a shorter life cycle.)

More raindrops finally snapped us out of the cicada’s enchantment. As we stood up to stretch cramping legs and crooked backs, the vivid green hills and shrouding mists of the Moquah Barrens renewed our sense of awe. Master Naturalist students study everything from landscape-scale geology to the ephemeral lives of insects in their week-long course. The breadth of topics can be exhausting, but some words from a friend seem to create enough space in my heart for them all. He said, “The world is beautiful at all scales.”



All photos by Emily Stone.
For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open. 

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.



Friday, June 17, 2016

Oh Honey! or Encounter with a Mantidfly

High on a swooping, prairie-covered hill on the Sylvan Runkel State Preserve in far western Iowa, I knelt down among the prickly thatch of last year’s grass for a closer look at the plants. With one ear tuned to the botanist leading the hike, I examined new green life pushing up through the old. A splash of color on the gray-green foliage distracted me further. The black and yellow insect soon had my full attention. In an instant I was grateful that I hadn’t remembered to give back the bug bottle from the morning bug hike. I scooped up my discovery and capped it securely, tucking the treasure away in my backpack next to binoculars and a granola bar.

“Oh, honey!” exclaimed the entomologist much later, as I opened the golden-hued pill bottle in the high school cafeteria before the evening program of the Loess Hills Prairie Seminar. From my experience with her earlier in the day—hunting bugs on the native prairie in the Sylvan Runkel State Preserve in far western Iowa—I knew that this particular exclamation was a good sign.

MJ Hatfield, the entomologist, is a retired UPS driver who discovered insects by way of native plants. She brings the pure joy of a dedicated amateur to the pursuit of bug catching. This particular insect inspired her exclamations in part because of its chimeric appearance, but also due to its fascinating life habits, and the fact that she doesn’t see its kind very often.

The creature that stared back at us (or not, it’s hard to tell where they’re looking) was an insect mutt. Large front legs—reminiscent of a praying mantis—remained tucked up under a pointed chin and two giant eyes. The rest of the body, however, sported flashy black and yellow stripes like a paper wasp. Flipping through a big reference book on the silent auction table, MJ soon found its photo. “Climaciella brunnea is the most commonly encountered mantisfly in the northeast and across the continent,” read the caption.

Mantidflies are neither praying mantises nor flies. They belong in their own family, Mantispidae, and have quite the life story.

The large, spiny, praying mantis-like front legs of mantidflies are used to catch small insect prey when they land on a flower where the predator waits.
As adults, mantidflies mimic the flashy “danger here!” colors of paper wasps. The bright stripes warn birds that wasps are a hazardous snack. Using a technique we call “Batesian mimicry,” mantidflies, a harmless species, impersonate the warning signals of paper wasps to escape hungry birds who would try to eat them both. When threatened, a mantidfly may assume the curled-abdomen position of a stinging wasp or wave its abdomen in the air to advertise the warning colors.

Across its wide range, from British Columbia to Quebec, and south to Costa Rica, Climaciella brunnea adapts itself to mimic the various local species of stinging wasps. In another smart move, the mantidfly adults time their abundance for spring and early summer, when most of the birds out foraging are adults who’ve already learned to avoid wasps. You see, newly fledged birds need a learning period in which to discover the wisdom in avoiding black and yellow insects. Without that negative feedback, the mantidflies’ trickery won’t work. Therefore, mantidflies move on to another stage in their lifecycle before the midsummer fledging rush.

Female mantidflies lay clusters of 1,000 eggs on leaves or other surfaces. The eggs hatch in 11 to 30 days. The dangerous mission of the tiny larvae (should they choose to accept it) is to attach to a wolf spider and sneak into its egg sack. Similar to questing wood ticks, the larvae wave their tiny legs in the air until they sense a wolf spider and then leap onto the base of its abdomen.

Mantidflies need to end up on a female spider, but they aren’t choosy in this first phase. They ride around on their host—snacking on a little hemolymph (spider blood) for energy—until the spider finds a mate and begins copulation. At this point the larva will make sure it is on the female spider. The transfer needs to be swift, since female wolf spiders often cannibalize the males after copulation. It’s not wise to get caught in the middle of such a marital dispute!

Then, as Mama Wolf squirts out her eggs, and before she spins the tough silk sack around them, the larva wiggles in. Once inside the snug, well-provisioned hideaway, the mantidfly larva pierces the eggs and sucks them dry. After a while it pupates in the safety of the egg sack and emerges as an adult.

“Oh, honey!” MJ exclaimed again with another peak at our discovery. The day had proceeded from a splash of color on a leaf to a journey of learning and amazement. After all that, I think we may also have emerged—as friends.

View MJ’s record of the mantidfly here: http://bugguide.net/node/view/1236586


Self-taught entomologist MJ Hatfield (center) catches insects and spiders in a native prairie. 
Photo by Emily Stone.

The wasp mantidfly (Climaciella brunnea) shares the hunting weapons of a praying mantis and the warning coloration of a wasp. These fascinating creatures are harmless to humans, even when trapped in a pill bottle. Photo by Emily Stone

Friday, June 10, 2016

Field Trips!

“To begin our skit, I need a volunteer…with LOTS of energy!” From within the sea of second graders sitting cross-legged on the classroom floor, a forest of little arms shoots up. I choose a tiny girl in hot pink who’s been so eager to participate she’s blurted out comments several times during my field trip welcome spiel. Might as well harness that youthful energy!

Holding up a photo of a ruby-throated hummingbird, I introduce the class to the first character in our skit. Then I drape a shimmery green cape across her shoulders, tie a white bandana around her throat and send her, “Ruby,” zooming around the room. The next boy who volunteers gets a black “ninja” eye mask to match the coloration of a wood frog. My third request is for someone “willing to be a little silly,” and I clothes-pin a white felt tail with a black tip onto the back of her t-shirt and ask the “short-tailed weasel” to wiggle her tail for the audience.

To match our “Nature’s Calendar” exhibit, our school field trips this year are all about phenology. We use these three animals to talk about the timing of seasonal events on nature’s calendar that happen at about the same time every year.

The skit brings lots of giggles. Ruby dons gigantic aviator glasses for her spring and fall “migrations” around the room. The frog tosses eggs into a wetland bucket and holds his pee in the fall (to concentrate urea that will protect his cells from damage while he freezes over the winter). The weasel mama leads a trio of pups on a hunting expedition around the room in between multiple wardrobe changes from white to brown and back. Scene/season changes are punctuated by a flurry of notes on my tin “adventure” whistle.

When we break into smaller groups, half the class follows Elsa into the Nature’s Calendar exhibit. The Sounds of the Seasons display offers a chance for the students to listen to the chirps and wing beats of a hummingbird. In the spring diorama, kids spy on wood frogs hopping toward a woodland pool. The weasel mount poses realistically in the winter diorama, and kids get to touch examples of both its summer brown and winter white fur.

For a dash of seriousness, Elsa also breaks out a big yellow Sun and a small globe. With a flashlight, she demonstrates how the tilt of the Earth on its axis means that in winter we’re angled away from the Sun, and in summer we’re tipped toward it. That tilt, in combination with our annual trip around the Sun, gives us seasons.

Meanwhile, the other half of the class puts on their hummingbird wings and heads outside with me. A real hummer zooms overhead from the feeder to his favorite perch in the mountain ash tree. I use a stopwatch to time the kids flapping their “wings” for 10 seconds. A hummingbird can flap its wings 700 times in that period. Second graders…about 38.

Then I put the kids through the paces. We drink from flowers and grow new feathers in Mexico. Boys head north first, migrating across the Gulf of Mexico, grabbing a snack in the southern U.S., and flying on to Wisconsin. There they set up a territory on a baseball base and collect poker chip “spiders” for food. When the girls migrate a short time later, they have the fun of scaring a boy off his territory to get food for their chicks.

According to Laura Erickson, male hummingbirds may not even know where babies come from. They single-mindedly defend a patch of flowers against other nectar-lovers, though. As a result, there’s plenty of food available when the slightly bigger female briefly zooms away from her egg incubating duties, flashes her scary white tail spots at the male, and grabs a bite to eat.

Finally, when the chicks have fledged and everyone has migrated back to Mexico, I stop the game with the universal call of “FREEZE!” My first question, “Are you tired yet?” is answered with an emphatic “NO!” I, on the other hand, am exhausted!

We fly back into the classroom, and this time, become frogs. After learning to imitate the quacks of wood frogs, peeps of spring peepers, snores of leopard frogs and hmmms of bullfrogs, we put on a frog concert. Wood frogs begin. Peepers join in. Wood frogs stop. Leopard frogs start. Peepers go silent. Bullfrogs round out the summer. And, for a blip in fall, the peepers give their last notes before a silent blanket of snow covers the hibernating frogs once again.

For our final game, the kids become short-tailed weasels. They get to choose whether to be white or brown each round, and test their luck against the “dice of the seasons.” When a roll of the dice lands on white snow, all brown weasels die. When the dice lands on brown leaves, the white weasels perish. After three rounds, they’re all dead. Then we play a new round. This time, I don’t roll the dice, but turn it in order of our normal seasons. All weasels survive the year. The timing of individual events is important, we decide, but in nature, it’s even more important that related phenology events happen at the correct times. A white weasel without snow has a problem.
We don’t go any deeper into climate change or the issues of our times. It’s too early to burden these young minds with doom and gloom. But hopefully, through this roleplay, they develop an empathy with their natural neighbors and will someday work toward our mutual survival on this tilted planet we call home. I’m hopeful. After all, they do have LOTS of energy!

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

 
Third graders from Spooner, WI, pose for a class photo under our exhibit banner after learning all about the phenology of hummingbirds, frogs, and weasels. Photo by Emily Stone.

Friday, June 3, 2016

Tree Frogs Trilling

Brilliant white trilliums nodded in the breeze and black flies chased me through the woods. My knobby tires crunched over sand and rocks on the Hatchery Creek mountain bike trail near Hayward. From the dense, green tree canopy overhead, dozens of warblers, vireos, flycatchers, and scarlet tanagers belted out their beautiful (though aggressive) songs.

Curving along a contoured trail cut precariously into the hillside, I caught a glimpse of sparkling water out of the corner of my eye. A small wetland thrummed with life at the toe of the slope. Through the cacophony of birds, a new sound filtered into my consciousness. Somewhat bird-like, these short trills seemed to add to the heat and humidity of the morning. The first of the gray tree frogs had made their entrance in the symphony of spring!

Gray tree frogs freeze solid over the winter, just like wood frogs and spring peepers. They spend the winter as “frogsicles,” with over 80% of their body frozen, and breathing and heart beat suspended. Although they thaw out early in spring—at the same time as peepers and wood frogs—gray tree frogs need to build up their energy reserves before they can start the strenuous business of attracting females. In contrast, the other two frogs take only a few days to recover from hibernation and start singing.

As with most frogs and toads, females choose a mate based on the length and strength of the male’s call, as well as the quality of his territory. Therefore, it is worthwhile to a male frog to put a lot of energy into his in calling. Gray tree frogs spend most of the night shouting aerobically at about 60% of their maximum output. But when a female is near, they bump it up to near 100% for a short time.

In order to accomplish these athletic feats of song, male frogs and toads have highly developed body-trunk muscles. Packed with mitochondria, the powerhouses of the cells, the singing muscles have the capacity for high aerobic metabolism. Frogs and toads call for such a long time that their muscles must switch from burning carbs to burning fats, just like human endurance athletes. (I can only hope that my mountain bike ride is long enough to start burning some fat!)

Those muscles are used to drive air over the vocal chords, producing the surprisingly loud calls. Some frogs and toads can be as loud as a lawn mower. Luckily, they have an internal pressure system that keeps their own ear drums from vibrating excessively and therefore prevents hearing loss in the shouter himself. In contrast, the silent female frogs and toads have much less body muscle. Their specialization, after all, is quietly laying eggs.

The most intense frog choruses occur on warm, cloudy nights, from dusk to midnight. But the air temperature needs to be at least 60 degrees F for a tree frog to call, so the early singers often call during the warmer daylight hours instead.

As you might imagine, loudly calling tree frogs can be vulnerable to predators. That’s one reason they prefer to sing at night, under cover of darkness. Males stay hidden in thick plants next to the shallow ponds where they prefer to breed. Gray-green, bark-like patterns on their skin make excellent camouflage.  A tree branch overhanging the water is the perfect stage.

Large, moist toe pads covered in mucous glands create enough surface tension to support the frog’s body mass as it climbs a tree—or your window. Climbing not only allows them to access safe singing stages and avoid predators all summer, it is also their main mode of hunting. Gray tree frogs search for tasty insects, larvae, mites, spiders, and snails in the understory of wooded areas. They need a lot of food to fuel their spring chorus, and will even cannibalize a smaller tree frog if it fits in their mouth!

If a predator—like any number of birds, snakes, other frogs, and small mammals—goes after a tree frog, it will leap away, revealing bright yellow-orange skin on its inner thighs. The flash of aposematic coloration may startle the predator and allow the frog to escape.

Pedaling off down the trail in my own flash of color (neon yellow!), I didn’t stop to search for one of the well-camouflaged singers. The bugs would have eaten me alive. Away from the wetland, bird songs dominated the airwaves again. But the frogs were not forgotten.

Later that evening, after washing mud spatters off my calves and fixing a flat tire, I sat down with my phenology journal to record the day’s new seasonal sightings. Tree frogs topped the list, in company with least flycatchers, scarlet tanagers, and American toads. Closing the book and turning out the lamp, I let the noises of the house fade away. Then—through the open window—streamed the bird-like trill of a tree frog, singing near my neighborhood pond. The symphony of spring continues.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.



Gray tree frogs prefer to call under cover of darkness on warm nights. Early in spring they will call during the daytime, too, when temperatures rise above 60 degrees. Have you heard their vibrant trill? Photo by Larry Stone.

Friday, May 27, 2016

Mysterious Song in the Bog

Blinking in the bright light, we filed out of the dark hemlock grove onto the sunny bog boardwalk at the Forest Lodge Nature Trail. Little bubbles and strange noises rose from below as the boardwalk’s supports sank into the peat under the weight of 27 birders from the Chequamegon Bay Birding & Nature Festival.

We listened intently for a bit, scanning the tree line for flitting warblers. Already that morning we’d seen or heard at least 16 species of birds, and now-familiar calls rang through the trees. A black-throated green sang his “I am black-and-green” from one side while a blue-headed vireo fluted sweetly from across the way. Ovenbirds shouted their “teacher, Teacher, TEACHER!” from all directions.

And then, from the little clump of trees in the bog’s center, came a rich warble that made us pause. The complex song was a jumble of high-pitched notes, rising phrases, and short trills. Usually, I rely on mnemonic sayings from John Feith's Bird Song Ear Training Guide to pop into my head and guide my bird identification. But I’ve been playing the warbler section of the CD on repeat in my car for a month now, and no helpful mnemonic came to mind.

The voice reminded me a bit of a song sparrow, who also has a complex song, but begins with a distinctive 2-3 note introductory phrase. “Maids, maids put on your tea kettle-ettle,” says the CD helpfully. It also brought to mind the driving song of the winter wren, but without the same level of intensity.

Finally, someone got a fluttering glimpse of a brown-and-white streaked bird with a faint dark spot on its breast. Another birder matched that with his knowledge of sparrows who might live in a shrubby bog, and the name Lincoln’s sparrow floated around the group. Whipping out my brand-new smartphone with the Audubon birding app, I clumsily found the Lincoln’s sparrow entry and played a snippet of his song. A perfect match.

How many birders does it take to identify a Lincoln’s sparrow? Apparently 27.

Now the hunt was on. We scanned the cluster of trees and shrubs intently, waiting for some movement to give away his location. Suddenly, he flew up from the low thicket of leatherleaf and landed on the sparse branches of a little tamarack tree. Its soft, young needles framed him perfectly, showing off a bit of warm tan color among the brown streaks under his chin. Then swoop! He darted off toward a different brushy cluster of trees and belted out his (now familiar) song a few more times.

Lincoln’s sparrows aren’t very common throughout the eastern part of their range. With their population centered farther west, Lincoln’s sparrows don’t even pass through some eastern states like Florida and Georgia on their migration north from Central America. As a result, this secretive bird was a “lifer” for many of the group, meaning it was a species they’d never seen before, and they now could add it to their cumulative “life list.”

This bird of the brush breeds in northern and mountainous areas in scrubby, dense vegetation near water, usually above 3,000 feet in elevation. Lincoln’s sparrows are especially drawn to willow thickets for nesting. Northern Wisconsin is at the very southern edge of their breeding range, but this bog looks a lot like its preferred habitat, despite our much lower elevation at 1,400 feet above sea level.

While his song reminded me of the winter wren in some ways, it is completely different in others. The winter wren’s regional “accents” are enough to divide it into separate, though similar, species; the Lincoln’s sparrow has little geographical variation in its song. Scientists believe this is because juvenile Lincoln’s sparrows disperse far and wide, effectively homogenizing their population. Not much else is known about this sparrow, though, since its behavior, habitat, and similar male and female plumages make it difficult to study.

You can bet I’ll be checking back later, without a posse of 26 birders, to see if this vociferous little sparrow is a resident, or just passing through.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.


Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Lincoln's sparrows tend to hide in dense brush, where there brown streaks make great camouflage. Photo by Mike Daley.

Birders from the Chequamegon Bay Birding and Nature festival look for the singer of an unusual song in the bog on the Forest Lodge Nature Trail near Cable, WI. Photo by Larry Stone.

Friday, May 20, 2016

Winter Wren

The symphony of spring grows richer every day. Stepping out my front door this morning, a blast of birdsong overwhelmed my senses. The translucent, glowing greens and pinks of newborn leaves were muted by low, gray skies, but the warblers’ songs lit up my brain with a rainbow of synesthesia.

The upward buzz of the northern parula, who just arrived on May 12, (four days later than in 2015) sounds blue-gray with yellow and orange highlights. The sweet warble of a Blackburnian warbler sounds blaze orange as it ends in a high pitch I can barely hear. The “I, am, black-and-green” song of the black-throated green warbler sounds (what else?) like alternating dashes of black and olive.

Ok, so maybe I don’t have synesthesia, maybe it’s only that the bird songs trigger their photos in my mind, but the dreary morning felt decidedly colorful with the addition of so many perky songs.

These warblers are not known for being quiet. And yet, when the winter wren chimed in with his ringing, clear stream of tinkling notes, the other songs faded into a background jumble. This four-inch-long, one-half-ounce, drab-brown bird of the forest floor can sing with 10 times more power than a crowing rooster per unit weight. He’s been singing here for weeks now (only needing to migrate from the southern U.S.), and—although I’m excited for the new arrivals—his song still gives me a thrill.

Partly, I (and the lady wrens) am drawn to him by the power of his song, which can last up to 8 seconds as he bellows notes while both exhaling and inhaling. Party, I’m intrigued by the mystique of this tiny, well-camouflaged bird that spends his time scurrying through the underbrush with mouse-like hops. The scientific name of the winter wren (Troglodytes hiemalis) means winter-loving cave-dweller, but their caves are hollows and cavities in dead and fallen trees.

What do they look like?  A little brown blur that sometimes congeals into a short, perky, twitching tail. Only through the patience of photographers do I know that they have tiny, white checkers on their brown background, a white eyebrow, and light-brown legs.

My favorite birds are the ones who kept me company during my transient years, when I worked back and forth across the county from California to Maine. I didn’t grow up hearing winter wrens in Iowa (house wrens are more common there). I first knowingly heard one in the Boundary Waters of northern Minnesota, which automatically endeared them to my heart. On still mornings, their energetic songs would resound across glassy lakes.

When I moved to the redwoods of California, my morning jogging route took me right past the territory of a wren near a tiny stream. They love riparian areas with tangled underbrush. It was exciting—in such a drastically different forest—to hear a bird I recognized easily. I was also thrilled to hear the familiar voices of song sparrows while we took kids tide-pooling along the ocean.

The song sparrows didn’t sound quite like the ones I was used to back east, although their tone and cadence were quite identifiable. It’s well known that many birds, like people, have regional variations in their songs. A Minnesota friend who recently headed to West Virginia for a birding trip joked that she’d be hearing warblers with southern accents.

The winter wren song sounds like such a jumble to me that I can’t hear the regional variation. The lady wrens can hear it, though. Several years ago, a couple scientists set out to study the variations in several subspecies of winter wrens across the country. Birders had already noted that the wrens in the eastern U.S. sound more like wrens in England, and the western wrens share more characteristics with their colleagues from Siberia. They are a widely distributed species!

Or are they? Where the eastern and western types meet in eastern British Columbia, they hold neighboring territories. The males will respond to any wren’s song with territorial aggression, but the females only mate with males who sing the appropriate song. I’ve tried to hear the difference, but the nuances are lost on me. Only by looking at sonograms (technological synesthesia!) can I be as discerning as those lady wrens. You can see them for yourself, and read an excellent summary of the research at: www.slybird.blogspot.com/2008/07/winter-wren-is-multiple-species.html.

The discriminating taste of those female wrens seems to be all that’s keeping the two types from hybridizing. Scientists call this a “prezygotic barrier to gene flow,” because it prevents mating in the first place. Mating would actually result in fertile offspring, should it occur. This seems tenuous, but it is a strong enough divide that in 2010, scientists classified the birds as separate species: the Pacific wren and our winter wren. England and Europe also get their own species of winter wren, which, as the only wren outside of North America, they just call a “wren.”

And, seeing as how I wouldn’t last a minute trying to be a discerning lady wren, I will just call him a lovely sign of spring.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Winter wrens are tiny, energetic birds of the forest floor. Ounce for ounce, they produce more sound than a rooster!  Photo by Paul Stein, Creative Commons

Friday, May 13, 2016

Spring Phenology

Birdsong and sunshine poured through open windows this morning, wafted in on a warm breeze. It was the distinctive call of a black-throated green warbler that finally lured me outside. “Zee-zee-zee zoot-zee” he shouted. “This is my territory and don’t forget it!” “Welcome home!” I felt like yelling back.

Several other melodies joined his refrain: the trill of a yellow-rumped warbler (a song I’ve been hearing for a few weeks already); the “Hey Sweetie” of a black-capped chickadee (I’ve been hearing that since January); and the tinkling stream of clear notes bellowed out by a winter wren with incredible breath control and no desire to let you get a word in edgewise. A pair of phoebes, and a few other mystery birds, also contributed their verses to the epic ballad of spring.

As I scanned the treetops to catch a glimpse of the feathered minstrels, I noticed with dismay that the maple trees were glowing brightly with tiny, translucent baby leaves among big clusters of dangling flowers. New life is beautiful, but leaf-out makes birding that much harder. I also heaved a sigh at the swarm of freshly-hatched black flies vying for my blood. Some signs of spring are not so pleasant.

It’s good for the migrating warblers, though, that the insects (and food for the insects) the birds need to eat are hatched and/or growing. When the long-distance migrant birds react to changing day length in South America and start their journey north, they have no way of knowing what weather will await them on the next continent. If we have an early spring up here, they can’t get bumped up to an earlier flight. If we have a late spring, they don’t get a text notifying them that their flight has been delayed.

These long-distance migrants tend to arrive like clockwork each spring, with very little change in their arrival dates. What variability occurs is mediated by the weather. As the birds head toward their breeding grounds, storms and lack of food will slow them down in a late spring, while favorable conditions will encourage steady progress north in an early spring.

While the weather this spring has been lovely for a few weeks now, this is the first morning I’ve heard the black-throated green warbler, who started its journey in Central America. The yellow-rumped warblers (here for a while now) may have only been wintering in the southern U.S. The blackburnian warbler (a striking, bright-orange firecracker) is still on its even longer journey from South America. It will probably arrive on about the same day it did in 2013 (May 15) even though that was the year I went cross-country skiing for my 50th day of the year on May 4.

In the meantime, the plants (who can’t go south for the winter) are controlled more closely by spring temperatures—although some regulation by day length plays a role in protecting them from blooming during a January thaw. I just photographed a plethora of spring flowers at St. Peter’s Dome. On Mother’s Day weekend 2013, I was snowed on while searching out a few spikes of furled leaves just emerging along that trail.

2013 was a great year for birding, though, because the birds came back all at once before the trees had a chance to leaf out. Visibility was amazing! Food-finding was probably a challenge for the birds, though, since local insects are also more responsive to temperature than day length.

Spring weather is always variable, but as climate change strengthens, the variability will trend earlier. Short-distance migrants might be able to shift their patterns and stay in sync with plants and insects on their breeding grounds. Researchers have found that the adaptation doesn’t happen within individuals, though. Individual birds arrive at the same time, year after year. Instead, natural selection favors the birds that are programmed to arrive earlier. They have more babies with similar, early genes, while the genes of their late-arriving peers go back to the dust.

I’ve seen a similar sentiment in a political meme floating around the internet right now, a quote by Arturo Albergati: "People don't change their minds. They die, and are replaced by people with different opinions.” While this seems a little morbid as I stand surrounded by glowing, singing, flowering, buzzing life in the most vivid season of the year, that adaptation through natural selection is actually a key to the future of life.

Observing seasonal events is also known as phenology. Come visit the Museum’s brand-new exhibit about phenology: “Nature’s Calendar: Signs of the Seasons” to learn more! Check our Calendar of Events for phenology journaling programs to inspire you to record seasonal events from year to year.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new phenology exhibit: “Nature’s Calendar: Signs of the Seasons” is now open.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Birders are often torn in spring. We want the migrants to have enough food when they pass through or arrive on territories, but we also prefer to be out with the woods unaccompanied by the birds' food source: black flies and mosquitoes. In addition, once tree leaves expand, birds become harder to see. Photo by Emily Stone. 
(I think this is a house finch. What do you think?)

Yellow-rumped warblers have been vocal and visible for several weeks already. He's so handsome!!! Photo by Emily Stone -- from a moving canoe!