A Northwoods Almanac for 1/22 - 2/4/21
Winter Severity Index
Prior to 1975, Wisconsin didn’t have a simple means for measuring the severity of winter’s impact on deer herds. Out of that need arose Wisconsin’s winter severity index (WSI), which uses the number of days with a minimum temperature of zero degrees F or below to measure winter cold, and the number of days with 18 inches or more of snow depth to estimate the impact of deep snow. Days when both conditions occur are scored as 2, or are scored as 1 if only one of the conditions occur, and are added from December 1st through April 30th to obtain the WSI.
The temperature and snow data is collected at 35 DNR stations across the north, but prior to the winter of 1986–87, the WSI was calculated from 12 United States Department of Commerce weather stations.
The total scores are then interpreted as “mild” if the WSI is less than 50, “moderate” if between 50 and 80, “severe” if between 80 and 100, and “very severe” if the WSI exceeds 100. These designations were arrived at based on observed associations between the WSI and winter mortality, fawn production, and buck harvest during the following year.
By looking at the numbers, it’s clear that severe and very severe winter conditions were common across the northern forest region from the early 1960s through the late 1980s, whereas mild and moderate winter conditions have mostly prevailed across the region since the early 1990s (see the chart).
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| WSI chart |
It’s important, however, to note how local habitat and winter conditions vary throughout northern Wisconsin. Deer in better habitats as well as deer subjected to milder conditions are typically less effected by winter weather.
As an example of local variability of weather, for the 2019-20 winter, the average WSI for northern Wisconsin stations was 65, which is considered moderate overall for northern Wisconsin. But in areas of farthest northern Wisconsin, “very severe” conditions occurred. Trout Lake in Vilas County and Gile in northern Iron County had the highest WSIs at 138 and 137, respectively. Other sites with very severe (100 or higher) readings were Mercer at 128, Pence (116), Washburn (112), Eagle River (110) and Cornucopia (105).
But many other northern sites relatively close to these areas received moderate readings, including Clam Lake (77), Florence (57) and Antigo (56), and others, such as Park Falls (49), Gordon (49) and Hayward (30), were rated as mild.
The winter of 2013-14, which most of us remember less than fondly, featured an average WSI of 143, and was the worst recorded in the 60-year history of the WSI.
So far, our winter of 2020-21 has been exceedingly mild with only a few nights in the Lakeland area dipping below zero, and virtually no areas that I’m aware of exceeding 18” of snow currently on the ground. As of now, we have a score of perhaps 4.
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| doe eating crabapples on the ground with little snow cover, photo by John Bates |
A mild winter like this isn’t only good for deer survival and reproduction, but also for many wildlife species. According to Ryan Brady, conservation biologist for the WDNR in Ashland, our mild, dry weather has allowed some bird species to linger much longer or in higher numbers than usual. For instance, at our feeders in Manitowish, we still have a red-winged blackbird, a common grackle, and a tree sparrow who should all have been gone long ago. Brady notes that almost every waterfowl species can be found somewhere in the state due to unexpectedly open waters, and American robins are overwintering in many areas where fruits and/or wet seepages are available. A Baltimore oriole is being seen in Marathon County and a rose-breasted grosbeak in Ashland County. And at least eight great gray owls have been documented in Wisconsin since November, our highest state total of this boreal species since the mid-2000s.
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| Great gray owl photo by John Bates in 2004 |
Most remarkable locally is the sighting on 1/16 of an indigo bunting at feeders off of County O on the border of the U.P.
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| Indigo bunting rang map |
Tim Feathers, owner of Whispering Point Photography in Weston, sent me photographs of the bird, and apparently it’s doing just fine. Indigo buntings typically winter in Central America, so hanging out in the town of Winchester is way out of its normal range.
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| Indigo bunting photo by Tim Feathers |
Sightings - Redpolls, Ermines, Great Horned Owls, Beavers
Common redpolls are living up to their “common” name this winter. Bruce Bacon, a master bird bander who lives just north of Mercer, banded 46 redpolls at his feeders on 1/13 and has banded a total of 118 redpolls so far this winter. Observing his feeders, Bruce estimates about half are banded, so he figures he has had around 240 redpolls visiting his feeders this winter.
If you’re not familiar with redpolls, the common redpoll gets its name from the small patch of red on its forehead. Males can be distinguished from females by the amount of rose color splashed across their breasts, while both sexes feature a black, goatee-like patch under their chin. I think of them as little Frenchies with red berets and goatees.
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| common redpoll photo by Bev Engstrom |
But they’re tough little Frenchies. They’ve evolved to deal with extreme winter conditions by burrowing into deep snow and making a foot-long tunnel to create a roosting chamber to stay warm during long nights. Studies on captive common redpolls in Alaska found that they can survive to temperatures as low as 65 degrees below zero.
Rod Sharka sent me a note after reading my last column about long-tailed weasels. He wrote, “We also have an ermine (long-tailed weasel) actually living under our front deck. I have observed this one eating the roasted peanuts being thrown out of the satellite bird feeder by choosy nuthatches. My wife, Myrtle, took the attached photo today when she spotted the ermine peeking out while she was filling the feeder with fresh peanuts.”
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| long-tailed weasel photo by Myrtle Sharka |
While walking along a couple lakeshores recently, we noticed beaver lodges with their winter food caches protruding from the ice in front of the lodges. Typically, winter food caches are made up of aspen, birch, alder, and willow shrubs. According to biologist Lynn Rogers, throughout the winter beavers swim out underwater from their lodges, nip off branches from the cache, then bring them inside and eat the thin bark - the cambium. Cellulose is very difficult to digest, and in the first go-round, microorganisms in their intestines can only digest about 30% of the cambium’s cellulose. This forces beavers to eat their own fecal pellets in order to extract more nutrients, a practice also common to rabbits and some other browsers.
Great horned owl hooting activity is peaking as pairs get ready to nest in late February and March. We’ve heard them numerous times over the years, but not yet this year.
2020 Tied for Warmest Year in Recorded History
Various analyses of last year’s global temperatures found that 2020 tied 2016 for the warmest year in recorded history. Adding in the 2020 results, the last seven years have been the warmest since the beginning of modern record-keeping nearly a century and a half ago. The scientists involved in this data collection universally agree that it’s because of greenhouse gases being pumped into the atmosphere.
Earth has warmed about 2 degrees Fahrenheit since the late 1800s, when the spread of industrialization began to lead to rising emissions of carbon dioxide and other greenhouse gases. Parts of the globe are also warming faster than others. Earth’s warming trends are most pronounced in the Arctic which is warming at more than three times as fast as the rest of the globe - see https://climate.nasa.gov.
The numbers are only a small part of the story. As climate scientists have predicted, the world is seeing an increase in heat waves, storms and other extreme weather resulting in disasters like droughts, floods and wildfires, including record fires in Australia and California, and severe drought in central South America and the American Southwest. An astonishing 22 separate weather and climate disasters costing over $1 billion each occurred in the US in 2020, shattering the annual record of 16 costly disasters in both 2011 and 2017.
This is the sixth year in a row that the US has experienced 10 or more separate billion-dollar disasters.
If you still question whether climate change is real, just ask the insurance companies who have to pay for these disasters. The insurer AXA has been surveying insurance risk professionals for five years on their key emerging risks. Climate change has always ranked high. But 2019’s survey produced a stunning result: Of the 1,235 risk professionals who answered the survey, the percentage of respondents pointing to climate change as their key concern rocketed up from 39 percent to 63 percent - see https://riskandinsurance.com/climate-change-key-risk-management-worry/.
Celestial Events
January 26 marks, on average, the last of the year’s coldest temperatures - a high of 21° and a low of 3°. We’ll see if that holds true. So far, January has been more of a lamb than a lion.
The “Wolf” or “Frost in Teepee” full moon occurs on 1/28.
As of 1/31, our days are now growing longer by 3 minutes per day.
February 2nd is, of course, Groundhog’s Day, when groundhogs in our area, those in their right minds that is, will absolutely not emerge from their dens to see or not see their shadows.
More importantly, February 3rd marks the mid-point between winter solstice and spring equinox, which to be honest, means little in terms of the winter weather we should continue to expect into at least late April and likely early May.
Thought for the Week
It is the small everyday deeds of ordinary folk that keep the darkness at bay. Small acts of kindness and love. - Gandalf, via J.R.R. Tolkien
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