A Northwoods Almanac for 1/19/18

A Northwoods Almanac for 1/19 – 2/1/18  

The Cold Facts

            We certainly experienced a cold stretch of weather over the last 3+ weeks, though the forecast for this weekend is a warming trend. Two thoughts about the cold we had: one, the -20° that we hit a few times is not particularly extreme for northern Wisconsin. Zone 3 for gardening and farming is defined as winter temperatures reaching between -30° and -40°, while zone 4 temperatures stretch between -20° and -30°. So, -20° barely puts us into zone 4. Our area, at least until the last decade, had always been designated as zone 3. Now that our winter extreme temperatures have moderated, we’re considered zone 4.

            My second thought regards the relationship between snow cover and intense cold.

Fresh, uncompacted powder snow typically is 90 to 95 percent trapped air. Many small animals take advantage of snow's insulating qualities and live throughout the winter in this “subnivean” zone. Once the snow cover has reached a depth of 8 inches or more, the subnivean zone maintains a temperature of close to 32 °F regardless of the temperature above the snow cover.

Diane Kappel-Smith, a Vermont naturalist and writer, describes this as the “winter threshold, and then the underworld begins a time of sheltered calm and darkness.”

The subnivean zone begins to form after the first accumulating snowfall. When snow lands directly on standing vegetation, downed logs and branches, and overhanging rocks, they act as umbrellas, creating protected areas for animals to move about.

Meanwhile, the snow that lands on the ground changes from a solid into a gas without melting, a process called sublimation. Twelve feet down into the soil in a normal snow year, it is warmer in January than in June. The stored solar heat and the geothermal heat rising from the core of the earth is trapped by the snow layer. This heat vaporizes the bottom of the pack, creating delicate, rounded crystals, or “depth hoar.”

In terms of insulation value, light snow is comparable to dry peat, fiberglass, or blown cellulose, because of all the air spaces it contains. If only it wouldn't melt, snow would make a great insulating material for buildings.

Snow Roosting

            Callie and I were snowshoeing in the Frog Lake and Pines State Natural Area over the weekend when my sister-in-law’s young Australian shepherd startled a ruffed grouse out of its snow roost just ten feet off the trail. The grouse exploded from the snow and certainly woke us from any reverie. I know folks who have stepped near a snow-roosting grouse and nearly had a heart attack when the bird burst from the snow beneath their feet.

            Like the small mammals I wrote about in the subnivean zone, grouse learned a long time ago of the insulating value of snow. With their wings and feet, grouse may extend their snow roost up to 10 feet to make a comfy little condo for themselves under the snow.

Common redpolls are known to also roost under the snow. Their tunnels may be more than a foot long and four inches under the insulating snow, says the Cornell Lab of Ornithology.

The Bear Facts

Deane Galloway noted in an earlier column that I stated “The Wisconsin bear population is estimated at 20,400 and has grown on average 3.4% annually since 1988.” I was quoting from a July 2017 Milwaukee Journal article that doesn’t jive with a much higher number – over 28,000 estimated in the fall of 2017 – which is the number currently used by the DNR. I don’t know which one is more accurate, but whatever the number, Wisconsin’s black bears are clearly thriving.

The full moon in January has been called by some the “bear moon” because black bear cubs are typically born in January. Sows now average giving birth to three in a litter, which sounds like a lot of work except for the fact the cubs are tiny, weighing less than a pound each. This makes the cubs smaller relative to their mother’s size than the young of any other placental mammal.

In a month, the cubs will weigh two to three pounds, and will have grown fur almost an inch long. Mother’s milk is their only food, and they get an exceptionally rich formula – 33% milkfat compared to a human mother’s 3%.

It’s cold in the den given that most den entrances are open to the air, so the tiny newborn cubs are kept very close to the mother. When they defecate, she eats the feces to keep the den clean and recycles the unabsorbed nutrients for her own use. 

Two “Wisconsin” Snowy Owls Fitted with Transmitters

            On December 30, a day with a high of 1° and 25 to 30 mile-per-hour winds, a female snowy owl, now nicknamed “Badger,” was caught and fitted with a transmitter near Freedom in Outagamie County.

Then on January 4, two juvenile male snowies were caught just south of the village of Arlington in southern Columbia County. Because like most raptors, snowy owl males are smaller than the females, one of the birds was deemed too small for a transmitter and set free. But the second male, which weighed more than 4 pounds, was an ideal size for a transmitter. Nicknamed “Arlington” for the town, he’s now “on line” and being followed wherever he goes.

While radio-collaring animals is relatively common these days, these aren’t any old run-of-the-mill transmitters. Solar-powered, they record locations in three dimensions (latitude, longitude and altitude) at intervals as short as every 30 seconds, providing exquisite detail on the movements of these birds. Unlike conventional transmitters, which report their data via Argos satellites in orbit, GSM transmitters use the cellular phone network. When the bird is out of range of a cell tower, the transmitters can store up to 100,000 locations, then transmit that information – even years later – when the bird flies within cell coverage. Once the owls migrate north beyond the limit of the Canadian cell phone system, direct contact is lost. However, their transmitters continue to log precise GPS locations, storing them until the owls migrate south the next winter (or the next, or the one after that). This information represents the most detailed record ever made of the movement of owls in the Arctic and subarctic.

The transmitters weigh about as much as seven U.S. quarters, but only 1.5 to 3 percent of the bird’s weight. They’re attached with a backpack harness that goes over the bird’s wings, a method that has not impacted mortality or decreased breeding success.

Previous transmitter data has shown how some snowy owls move out onto the frozen surface of the Great Lakes for weeks or months at a time, apparently hunting for waterfowl using cracks in the wind-driven sheets of ice. The data has also confirmed that snowy owls feed heavily on birds in the winter, especially ducks, geese, grebes and gulls, and for the first time the owls have been documented hunting at night over the open ocean, often using channel markers and buoys as hunting perches.

The researchers have already learned that one of our Wisconsin snowy owls, “Badger,” has remained in a 0.7 square mile area since she was tagged over two weeks ago.

The Natural Resources Foundation of Wisconsin and Wisconsin Public Service Foundation have sponsored two of the transmitters, Madison Audubon Society is sponsoring another, and the Wisconsin Society for Ornithology is funding a fourth.

Sightings

            Denise Fauntleroy sent me a photo of a flying squirrel eating the Christmas popcorn she had strung on a tree outside her window. With a spotlight on the tree at night, she has watched them at length. She didn’t say, however, if they ate the strung cranberries.

photo by Denise Fauntleroy

            Along those lines, Mary, Nancy Burns, and I were snowshoeing on the WinMan trails last week when Mary saw a movement in a tree near the trail. Something was working its way high up the trunk of the tree, and at first Mary thought it was a brown creeper. But it suddenly leapt from the tree and glided to the next tree. Mary hollered for me to catch up to her and as soon as I did, what turned out to be a flying squirrel leapt again into the air and glided away from us toward the ground. This was the first time during the day I had ever seen a flying squirrel in flight!

            We have an entertaining flock of at least 14 pine grosbeaks working our feeders every morning. Besides their beautiful coloration, they also consistently sing, which in the quiet of winter is a very pleasant addition to anyone’s yard.

            This winter continues to bring good numbers of common redpolls and pine siskins to local feeders, but so far few to none of evening grosbeaks, bohemian waxwings, or purple finches.

Celestial Events

            Here’s something to look forward to: January 26 marks the last of the year’s coldest average high temperature: 21°. It’s also the last of the year’s average coldest days. So, everything, on average, should be getting warmer now. Of course, the problem with averages is illustrated well by this quote from Bruce Grossman: “A statistician is a person who lays with his head in an oven and his feet in a deep freeze stating, “On the average, I feel comfortable.”

            We’re up to 9 hours and 31 minutes of daylight on January 27.

            The full blue supermoon occurs on 1/31. To see the total lunar eclipse that same day, you’ll need to be up early at 5:48 a.m. to watch the shadow begin to sweep across the moon from left to right. Totality begins at 6:51, but the oncoming light from the sunrise will diminish the effect.

Thought for the Week

            Nature is party to all our deals and decisions, and she has more votes, a longer memory, and a sterner sense of justice than we do.  – Wendell Berry