Overcast and cold this morning, out on the recovering prairie lands of Midewin. About 27 degrees, with a slight wind making it feel more like 21. Perfect weather for marveling at the hardiness of birds and bison, alike.
Bison, of course, are legendary for their ability to withstand the frigid temps and deep snows. The 27 bison that arrived at Midewin a few months ago appear to be adapting well to their first Illinois winter. The snow cover thus far has been thin, which means they haven’t yet needed to use their massive heads as snow plows to access the grasses upon which they feed.
As for the cold, well, a temperature in the 20s is practically beach weather for bison. In the winter, bison sport two kinds of hair – an outer layer of course, thick hair, and an inner layer of soft, fine hair. I know a little about the inner layer – my scarf if made from yarn spun from this source. It is the warmest, softest scarf I have ever owned. (It also holds a little sentimental value for having been knitted by Marta Witt, a former chief information officer for the US Forest Service, stationed at Midewin.)
To get down to the science of it, bison fibers have a micron count of 15. A micron is one-millionth of a meter. The lower the micron count, the softer, the warmer the fiber. Most wool fibers range between 23 and 27 microns. Cashmere, the softest fiber in the world, beats bison by only, well, a hair, clocking in at 14 microns. And like cashmere, bison contains no lanolin, which renders it hypo-allergenic.
OK. Weighing a ton and wearing, essentially, thick blankets of insulation, it’s easy to imagine how bison survive the winter on the open prairie.
But what about birds? What about downy woodpeckers, for instance, that weigh no more than an ounce, or about the equivalent of a first class letter? How is it possible that they survive even five minutes, let alone an entire winter season?
Well, as it turns out, feathers are the most naturally insulative material on earth. Think down jackets, and how they trap countless pockets of air to keep their wearers warm. On average, small birds are covered by an astonishing 2,000 to 4,000 feathers, most of which are entirely downy in structure. Tucked safely beneath contour feathers, which are waterproof, they provide – to use sleeping bag insulation parlance – a lot of “loft.” Or, to use the construction industry’s term, a high “R-value.” Or, in layman’s terms, a lot of warmth.
Me, curious mammal that I am, the only way I’m enduring even two hours of cold this morning is to layer up my mostly hairless and entirely featherless body with a wicking t-shirt, a thermal long sleeved shirt, a cotton turtleneck, a cotton hooded sweatshirt and an insulated leather coat; plus, of course, gloves, hat and that awesome bison scarf.