Frozen Flows

The surface of the Superior Hiking Trail alternated between dry pine needles and compacted ice as we followed it into the woods. With clear blue skies the day before, temperatures had plummeted into the teens overnight, and were now rising quickly again under the discontinuous cover of wispy clouds. I can’t help but repeat the refrain…what a weird winter!

As our world changes, I’m grieving my old friends cross-country skiing (on natural snow) and the subnivean zone, while still making a point to appreciate new delights. I can’t even count how many times I’ve looked at the frozen surface of a North Shore river and wanted to walk the whimsical ice formations up through bedrock canyons. But on past visits the snow was too deep, the wind chill too brutally cold, or the skiing too good to choose that adventure.

This past weekend, conditions were finally perfect! Temperatures have been just cold enough overnight to solidify the ice over the shallow waters of the Kadunce River. The thin snow cover facilitates that by not insulating ice against the nighttime freeze. The skiing is almost nonexistent, and the sunshine pleasantly warm. So, our shoes crunched lightly on the grippy coating of snow as we stepped down the bank from the dry path onto the trail of river ice.

I was a little surprised at how solid the ice felt, even when we stepped near patches of open water. In such a small, bony, stream, there’s a good chance that we were supported by rocks as well as water. It’s different on a lake. Something I choose not to think about very much is that when you drive a truck out on the ice to go fishing, you’re actually being supported by the water. The ice sags under your weight and displaces water equal to the truck’s mass, creating buoyancy. If the ice is brittle and cracks instead of deforming, your “boat” now has a hole and sinks.

On such a small river, we weren’t worried. I was fascinated, though, by the formations visible through the small ice “windows.” The surface was rippled and mixed with snow, while the lowest ice was tickled by the chuckling stream still flowing beneath. In between was a nice layer of columns, stalactites, and clusters of little bulbules.

Especially in a warm winter like this one, ice formation is a dynamic process. In a lake, the coldest water becomes less dense and rises toward the surface, where it freezes. In a stream, turbulence mixes the water and no layer of almost-freezing water can stay at the top. Instead, tiny crystals of frazil ice form, especially in the top inch or so of moving water, and tumble around. As air temperatures drop, the water temperatures decline, too, even going just below the freezing point. Once “supercooled,” the frazil crystals are primed to freeze to each other or to other surfaces. Ice attaches to rocks, the shore, or other frazil crystals, and spreads from there.

Admiring the lumpy but elegant ice covering a head-high waterfall, I guessed that it must also form by supercooled frazil ice first sticking to rocks and then to itself. Moving water still flickered under the thin shell.

The edge of the plunge pool under the waterfall was still open, where cold had not yet overcome turbulence. I was amazed, though, that much of the surface was frozen. Petrified ice pancakes were an indication of the iterative process of ice formation in this warm winter. When the plunge pool was more open, chunks of broken ice or clumps of frazil crystals would have been caught in the eddies and spun into each other, rounding all of their corners and creating a raised rim of slush. Then, the surface froze around this pancake ice.

Around the opening to several “breathing holes” where we listened to the sweet music of running water, delicate crystals of hoar frost added even more elegance. Water vapor in the air, rising from the liquid river, crystallized directly onto the chilled surface of the ice. Like snowflakes, the crystals of hoar frost grow with exquisite precision based on the chemistry of water.

Adding to the magic of the day were the vertical canyon walls. The Kadunce River cuts through an impressive formation of flow-banded rhyolite. About a billion years ago, an immense volcano many miles inland erupted so violently that a huge mass of ash tumbled toward what is now Lake Superior. The movement of the flow caused the formation of little layers or bands, and eventually the ash solidified into rhyolite. Now the river cuts downward through the rock and exposes pale pink walls with inch-thick bands.

From ancient rocks to frozen rivers, and even weird weather within the larger context of climate change, the Earth creates beauty in its own time.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through March 9. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Friends at our Feeders

I’ve been hearing a lot of complaints from people who are feeling lonely this winter. For once, they aren’t feeling cooped up by icy roads and constant blizzards. Instead, we miss our feathered friends! A suite of factors, including the nice weather, means that birds are not as abundant as usual at our backyard feeders.

My guess is that with shallow snow many birds are able to find food in the woods. Plus, the mild temperatures reduce the number of calories they require to stay warm. In addition, the grosbeaks, redpolls, and crossbills we love to see are “irruptive species.” To irrupt means to enter an area suddenly (in contrast to the lava erupting out of the volcano suddenly). We don’t see these irruptive species every winter, at least not in any quantity. Most migrations are driven by food availability, and these are no different. This year, their favorite foods are more abundant elsewhere.

One exception, at least at my feeders, are pine siskins. These stripey little finches with yellow highlights breed in the remote forests of Canada, as well as northern Wisconsin and Minnesota. When their typical winter food supplies in the north are low, pine siskins may flock into New England, the upper Midwest, or even the southeastern United States. They are looking for plentiful supplies of seeds from pines, cedars, larch, hemlock, spruce, alder, birch, and maple. I’m not sure what natural food is abundant this year, but my plentiful pine siskins seem to be enjoying a “sunflower chips” mix that has some hulled and some whole sunflower seeds.

Pine siskins put on more fat than many other little birds. They also fluff out their feathers and tuck up their toes to stay warm on frigid days. Photo by Emily Stone.

In fact, I’ve been observing that pine siskins are the most dominant birds at my feeder. They will hiss and spread their wings aggressively to prevent goldfinches, chickadees, and nuthatches from swooping in to grab one of those tasty sunflower seeds.

By eating all those seeds, pine siskins put on 50 percent more winter fat than their cousins—common redpolls and American goldfinches. Little birds don’t store fat in an insulating layer of blubber like penguins and whales; they accumulate stores of brown fat around their wishbone and abdomen as a ready source of fuel for their metabolisms. Siskins also store a bedtime snack right in their esophagus—in the expandable section called the “crop.” But it isn’t just a single cookie and glass of milk; their crop can store seeds equal to 10 percent of their body mass.

Those calories could get them through five or six hours of sub-zero temperatures. They can survive negative 94 degree Fahrenheit nights by revving up their metabolic rate to five times normal for several hours. That’s 40% higher than other songbirds.

Why don’t more little birds put on that much fat for winter? Getting too fat can make it harder and more energetically costly to fly, and reduce their ability to escape predators. Chickadees may only achieve 10 percent body fat in the winter. Instead, chickadees store food. They cache up to 100,000 food items per year – most of them in the winter. In order to remember all of those caches, chickadees add new neurons for every hidden seed, berry, or insect. The result is a 30 percent increase in brain volume, which shrinks again during the easy-living days of summer.

Besides adding a little fat and a lot of neurons, chickadees grow 12 percent more feathers for winter insulation. That’s nothing compared to common redpolls, who add 31 percent more feathers! That’s a big increase for a bird that only weighs half an ounce to begin with. Why don’t more birds add that many feathers? During a Wild About Winter Ecology Workshop years ago, Prof. Sheldon Cooper from UW Oshkosh compared small birds adding feathers to putting a toddler in a snowsuit. A big being, like a snowy owl or an adult human, can still move pretty well, even if you add some puffy layers. The smaller the being, though, the more those layers can impede movement.

From fat to feathers, all winter adaptations have their pros and cons, just like this weirdly warm winter we’re having. If the birds have left you feeling lonely, take advantage of the clear roads and visit a human friend instead!

Author’s Note: Portions of this article are reprinted from 2014 and 2019.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through March 9. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Warm Winter Worries

What a weird winter! In a region where people love to talk about the weather, the chatter has been constant. Skiers and snowmobilers (and the business they support) are particularly grumpy, but many people are trying to make the best of pleasant temperatures, despite the lack of snow. Humans are lucky. We have temperature-controlled homes and clothing that can be changed at the drop of a hat.

But what about non-human beings? How are they faring as temperatures fluctuate from 50 degrees to the teens with barely a skim of snow on the ground? This week, I combed back through my many articles about animals in winter to try and understand what some of the impacts may be.

In a typical winter, when we have at least six inches of snow, The Subnivean Zone forms. Because of the insulating qualities of snow and leftover summer heat from the Earth, a thin zone opens up under the snow, right at the surface of the ground, which stays at a pretty stable 32 degrees Fahrenheit.

Ruffed grouse make use of this warm blanket. When the snow is deep enough, they “roost” by doing a swan dive, leaving no tracks that would lead a predator to their warm bed. Without snow, or with icy crust, grouse may struggle to find a warm roost.

Small mammals like mice, voles, and shrews lose more heat for their body size than big ones, and therefore must generate more heat to maintain a healthy body temperature of about 98 degrees. Dr. Paula Anich from Northland College has estimated that shrews burn twelve times more energy per unit of body mass than an elk. They are constantly racing toward the edge of starvation, and all of the little beings must eat pretty much constantly to survive. Without snow, they face the choice of staying safe and warm in a burrow, or risking being eaten or getting too cold while they forage for food. “To the mouse, snow means freedom from want and fear,” wrote Aldo Leopold in A Sand County Almanac.

Even with snow, mice still need to fear American martens. These small weasels hunt along the log-lined runways where red-backed voles, mice, shrews, and squirrels travel. The snow is an excellent blanket for this lean mammal, who stores little fat and burns lots of fuel to stay warm. Snow also provides cover from bigger predators. The diets of foxes, fishers, and bobcats overlap with martens’ diets, and those larger carnivores will kill martens to eliminate competition.

Martens’ smaller cousins, least weasels, short-tailed weasels, and long-tailed weasels, all hunt under the snow as well. The subnivium is so important to Mustela nivalis, the least weasel, that their scientific name means “weasel of the snow.” These three fierce hunters need snow for an additional reason: their fur turns white in the winter, and a shift in the timing of snow cover can leave them vulnerable to their own predators.

Short-tailed weasels need snowy winters to match the camouflage of their white fur, and to provide safe, warm hunting grounds. Warm winters like this one will make it harder for them to survive. Photo by Emily Stone.

Autumn leaves can provide insulation before snow accumulates, and then continue to augment our fluffy white blankets. This protects plants’ roots from freeze damage. Dead leaves in the subnivium also provide essential habitat for woolly bear caterpillars, mourning cloak butterflies, luna moth cocoons, the eggs of red-banded hairstreaks, bumblebee queens, spiders, snails, millipedes, mites, and more. Some of these beings are frozen, some of them are active.

Wood frogs take refuge in leaf litter and very carefully allow themselves to freeze solid while the subnivean zone forms around them. Once frozen, their metabolisms are shut down, which preserves their limited energy stores. The moderating effects of the subnivium buffer them from energetically costly freeze-thaw cycles, and also reduce the potential for lethally low temperatures. After warmer winters, female wood frogs lay fewer eggs.

Like wood frogs, goldenrod gall fly larvae can freeze solid. They spend the winter in little round homes built inside goldenrod stems. While they can endure multiple freeze-thaw cycles over the winter, warmer temperatures increase their metabolism, and reduce their body size. When they hatch in the spring, the resulting adults – who do not feed – will not be able to lay as many eggs.

Beyond getting a break from shoveling, it’s not easy to find a silver lining for this weird weather. Here’s one possibility, though: deer ticks might suffer if a hard freeze comes while they are exposed without snow. If mice populations drop as well, then maybe there will be a decline in the spread of Lyme disease next summer. One can hope.

Jon Pauli, a winter ecologist from UW-Madison, once explained to me that “there's a complex ecosystem of interacting microbes, insects, plants and animals that we can't see but are active throughout the winter.” In fact, says one of his research papers, the subnivium is where the “majority of biodiversity in northern temperate areas spends the winter.” That’s why it’s so devastating when The Subnivean Zone doesn’t exist.

If you’d like to learn more about The Subnivean Zone, just wait until May 1st. Winter will be over, but the Museum’s new exhibit, Anaamaagon: Under the Snow, will give you an inside look at this special place.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through March 9. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Snowflake Stories

Snow crystals grow unique branches and facets as they travel through different habitats in winter clouds. Since each snow crystal is on their own journey, no two are exactly alike. Photo by Emily Stone.

“Snowflakes are amazing!” I gushed to the students in a recent “Words for Winter Wonder” writing workshop hosted by the Lake Superior Writers in Duluth, Minn.

I continued on, summarizing how snowflakes form. Water vapor crystalizes around a piece of dust, or dirt, or even a unique bacterium. Then, as puffs and gales of wind toss the nascent snow crystal inside a cloud, they experience varied combinations of temperature and humidity. The crystal grows differently in each new habitat. One environment produces simple hexagonal prisms. Another combination of characteristics builds beautiful branches. A snow crystal grown in just one habitat might be pretty basic, but the ones who cause us to gasp at their beauty when they land on our sleeve have traveled far and wide.

I clicked to the next slide, and a video of a single snow crystal growing in a science lab shone on the screen. The delicate beauty, even translated through all of that technology, was stunning.

http://www.snowcrystals.com/videos/videos.html 

“Now, we get to try to imitate that beauty that comes with variety,” I said as I passed out a different color of paper to each of the six students. How fitting, I thought, to have six students to imitate the six-sided snow crystals.

Each person wrote a single sentence (sometimes two, it’s hard to reign in writers) at the top of their paper. The instruction was simply to “set the scene.” When I told the students to crumple their paper into a ball, there was some worried chuckling. That turned to laughter when I yelled “snowball fight!” and the paper balls went flying across the room.

Each student picked up a ball that wasn’t their own, and now I added a new element to their environment. “Add the next sentence to the story on your new paper, but this time include visual descriptions, your sense of sight.” We wrote, crumpled, tossed, and flattened the papers over and over, adding sentences about touch, smell, and finally a conclusion. Then each student read aloud the story contained on their final (very wrinkled) paper.

The resulting winter vignettes were almost as beautiful as snow crystals formed high in a winter cloud. The tone for each one had been set by the original writer, and (just like with a growing snow crystal!) the subsequent additions were a mix of sticking to the story and adding each writer’s own flare. I’d like to share a few of them with you here.

1. The late afternoon sun lingered on the horizon, casting long shadows over the ice. No snow had yet fallen over the bubbled blue of new ice. The weak yellows of the sun barely colored the landscape. She lay on the smooth ice, feeling the frigid cold beneath her, staring below. The scent of dry leaves blew out from shore, but beneath that the air was clean, crisp, promising snow to come. She looked forward to seeing the ground covered with its clean white equality.

2. She stepped out her door into the chill, quiet night to watch the first snowflakes of winter. Through the muffling of this snowfall, she heard the light crunch of footsteps. She imagined how it would feel to wear those boots, to sense the leaves crackle under her feet with the snowflakes dissolving cold on her skin. Woodsmoke from a nearby cabin mingled with the snow in her hair, releasing an earthy fragrance. She saw the kind face of her neighbor come to greet her to share in this delight.

3. Large puffs of snow drifted down around her as she walked along a winding winter path. Each branch caught the flakes and held them as their dark branches whitened. As she passed a railing, she ran her mitted hand along it, gathering the cool, light snow in her palm. The winter air smelled white, burning her nose, and she burrowed into her woolly scarf, inhaling her own warmth. She was content here, though in a moment she would turn away toward home.

4. The fox came into our yard quietly, cocking his head and stopping frequently. He rolled in the fluffy snow sending dried seed heads of spent wildflowers flying into the air. The fox shook his fur as the seeds tickled his whiskers – enough playing around! He stopped cold – a whiff of something travelling downwind – something warm, sweet and enticing. Ah, a mouse nest under the snow, and a well-aimed pounce on winter snack!

As with snow crystals, no two snowflake stories will ever be just alike, and their beauty is a reflection of the community who created them. Thanks to my students for allowing me to share their stories with you!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through March 9. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Germinating Seeds and Excitement in Hawaii

Waves crashed onto the black sand beach at Waiʻānapanapa State Park near Hana, Hawaii. This was our final stop on the Road to Hana, and our last big adventure of the trip.

The black sand beach Waiʻānapanapa State Park was one of the last spectacular places we visited in Hawaii. Photo by Emily Stone.

From the high point overlooking a cove, my parents and I focused our binoculars on a cluster of seabirds sitting on a rock draped in some tough plants and white bird poop. Noio are an endemic subspecies of black noddy with pale gray tails and orange legs. While their cousins are global travelers of tropical and subtropical seas, noio arrived in Hawaii on their wings and then stayed.

Feeling adventurous, I descended several flights of stairs to the beach, wiggled my toes in the black sand, and then climbed a craggy cliff of young, black basalt on the far side. When a cluster of ferns caught my eye, I paused to look closer. The smooth fingers of the fronds reminded me of common polypody, a fern that often grows on top of boulders in the Northwoods. In the same family, this golden polypody fern could have arrived through spores blown on the wind, but my sources list it as introduced, so it probably arrived here through human interference.

At the top of the headlands, I stood in awe as waves crashed into the rocks and tossed salty spray high in the air.

Wings, wind, and humans are three of the most common ways that life has arrived on Hawaii since the volcanoes rose above the ocean. But besides the obvious humpback on a whale watch, I hadn’t noticed many who had arrived on the waves. As I descended the trail back to the black sand beach, a tiny white flower caught my eye. Recognizing it as Beach Naupaka, or Naupaka kahakai from my nature guide Wind, Wings, and Waves by Rick Sohren, I stopped to take photos.

Five white petals, each about 2 cm long, were lined with lovely wine-colored accents. The shape was what gave it away – the petals all drooped down, giving the appearance that this was only the lower half of the flower. There are many different folktales about Naupaka, which represent at least 9 species who grow both on the mountains and shorelines, and they all read a little bit like Romeo and Juliet, with star crossed lovers who will never be reunited until the flowers are made whole.

After checking out the succulent, oval, green leaves that surrounded the flowers, I suddenly realized that Naupaka was growing everywhere on the rocky cliffs! The low shrubs lazed about and crept over rocks on pale gray branches. Naupaka kahakai are great for shoreline stabilization, and may be the most widely used native plant in Hawaiian landscaping. Unfortunately, their robustness also makes them invasive in Florida, where they aren’t native.

I spotted a couple of white berries among the leaves. These berries are sometimes called Huahekili, which means "hailstones" in Hawaiian. While the Naupaka berries were famine food, they are said to be bitter and slimy. Inside the slimy berry flesh is where the real magic happens.

Naupaka kahakai seeds can float in seawater for more than a year and still manage to germinate once they land. Once ashore, they are very tolerant of salt spray, although not of being inundated daily. Lucky for them, Hawaii is so far out in the open ocean that it experiences relatively small tides.

Not only can Naupaka kahakai seeds survive seawater, they seem to need it for germination. One native plant guide suggested that soaking them in salt water made it easier to grow them from seed.

These durable – but picky – seeds reminded me of several others back home. The next generation of jack pine trees are squirreled away in sealed cones until fire softens the pitch and releases seeds onto freshly cooled ash. Raspberry seeds sprout best if their hard coats have been softened by stomach acids of a hungry bird or bear. Tiny, poppy-seed-sized columbine seeds can only germinate in the presence of light. Violet seeds prefer dark. And many of our native plants, including common milkweed, must experience several months of cool, damp “winter” conditions whether outside or in your refrigerator.

Jack pine cones are sealed shut with pitch and need fire (or a hot day) to open them. Photo by Emily Stone.

Likewise, the seeds of my excitement about Hawaii didn’t germinate quickly. I flew there (arriving on wings!) planning to check off my 50th state and visit a bunch of places I’d organized on a spreadsheet. Once there, I found myself exposed to impressive ocean vistas, soaking up the sun and tropical humidity, being fertilized with cool facts at every park, and being drawn out of my shell by the light of curiosity. After seven days in Hawaii, and two months writing about it, my appreciation for the state sprouted like a weed and is ready for another trip!

A rainbow on top of Haleakala

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through mid-March. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.