Tawny, dried weeds and their dusky shadows painted texture on the roadside border as I drove up Scenic 61 along Minnesota’s North Shore of Lake Superior. Suddenly, those colors came alive in a cloud of swirling beauty. Brilliant white, sharp black, brown, and blur; the flock of snow buntings ascended, swooped as if tossed by blizzard winds, flashed their colors in unison, then fluttered back to invisibility among the weeds.
These tough little visitors from the Arctic live up to their nickname of “snowflake birds.” Snow buntings nest on tundra all around the top of the globe, and are the most northerly recorded songbird in the world.
My toes get cold just thinking about it, but feathered feet allow snow buntings to spend most of their winter strutting about on the chilly drifts. They usually feed in big, gregarious flocks that seem to roll along chaotically as the birds in the back make short, fluttering flights to the front. Occasionally, the whole group will rise and fall in a flurry of motion at the suspicion and passing of danger. Feeding flocks are entertaining to watch, since these birds don’t submit to a defined hierarchy like chickadees do, and end up bickering continuously over seeds and space.
Deep snows cover up the seed heads of short tundra plants in their breeding territory, but here in the Northwoods, snowplows expose seeds in the gravel shoulder, and windswept fields of nodding stems offer good foraging, too. I was particularly happy to read that they eat seeds of the ragweed plant, which is a major cause of seasonal allergies!
While snowshoe hares turn white for the winter, snow buntings add brown and spend the season with rusty patches on their feathers. It helps them blend in on the bare fields and among the grass stems where they feed. By April, that color has worn off to reveal pure white plumage that will match their still-snowy Arctic breeding habitat. Since snow buntings nest in deep cracks and cavities in rocks to avoid predators, their nesting sites are limited. Not going too far south and arriving early back north to claim a territory is essential.
Their breeding is carefully timed so that chicks are hungriest right when insects are most plentiful. Warm springs that shift breeding earlier produce a mismatch with their food source. Hard winters seem to keep this timing well-matched. What type of winter will this one be?
Swirling flocks led me up the North Shore, all the way to the Cascade River north of Lutsen, MN. The trailhead was empty, and it looked like we were the first ones on that section of the Superior Hiking Trail. While cool, wet weather has made a lot of trails muddy recently, the ground was rock hard under my hiking shoes. Frozen! A novel experience for this fall, when September and October both set records for higher-than-average global temperatures.
Then: Crunch! Crunch! Crunch! The trail was filled with fragile clusters of ice, pushing up through the soil. My clumsy feet had pulverized some, but in several places the ice remained beautifully sculpted into ribboned clusters a few inches high. Squatting down for a better look, I noticed soil particles, moss fragments, and grass blades frozen into the ice.
“Needle ice” seems to be the most scientific term for this phenomenon, but I’ve also heard it called frost pillars, frost castles, and ice filaments. The Swedes, Germans, and Japanese have their own words for this circumboreal art form, too.
While not confined to one region or habitat, needle ice does require a certain set of conditions in order to form. First, the soil must not yet be frozen, at least beyond the first thin crust. In contrast, the air temperature needs to be below freezing. Finally, the soil needs to have plenty of moisture, and just the right sized pores between the grains so that water can flow toward the growing ice.
What draws the liquid water toward the ice is a process known as ice segregation. Supercooled water – held in a liquid state below 32 degrees F – moves toward ice and adds on to it. When the two meet, ice grows away from the ice/water interface. As the ice crystals expand upward, growing perpendicular to the surface, they may also push soil up or away, lift small pebbles into the air, and incorporate whatever debris is nearby. This fragile structure of ice and dirt is what crumbled under my hiking shoes.
I’m not the only source of destruction, though. Once these frosted soils melt, they are loose and susceptible to erosion. If the needle ice forms on a slope, even just the action of lifting soil particles up and letting them down again will cause them to descend in the process of soil creep. This is a challenge for trail maintenance.
The icy hike was beautiful, and “snowflake birds” swirled ahead of my car all the way home. Real snowflakes chased me from behind, and soon accumulated six inches of the white stuff. Snow buntings and needle ice foretold the coming winter, and as I write this, it has arrived!
Author’s note: portions of this article are reprinted from 2015, 2016, and 2022.
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.
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