Friday, November 21, 2014

Little Kings of the Winter Woods

A light wind rattled the oak leaves still clinging to their twigs, while my snowshoes crunched through the crust, and expanding lake ice sang eerily in the distance. So far my walk – a quest for inspiration – had yielded only cold cheeks and a stark winter woods.

Near the end of the trail, a new sound filtered gradually into my consciousness. High, thin, “see see” notes drifted down from the dense foliage of a little stand of fir trees. Chickadees! I thought at first, and smiled, although I did not look up. Then I caught a movement out of the corner of my eye. Just above my head, several little birds fluttered in the boughs. The seemed too delicate to be chickadees, their song really was too high and thin, so now I focused in on their field marks.

Instead of the black chin of a chickadee, I looked up at a creamy-colored throat and breast. Their backs and wings were warm olive with black and yellow markings. I started to develop a hunch for who might be in this little flock, but it took me several minutes of focused observation (of course I’d forgotten to carry binoculars) before one tipped her little head right toward me. Ah ha! A yellow stripe ran down the top of her head, black stripes surrounded it, with another black stripe through the eyes. Golden-crowned kinglet.

Now here was some inspiration. Golden-crowned kinglets are one of the smallest songbirds, and yet they commonly overwinter in places where the nighttime lows plummet to -40 degrees Fahrenheit. Bernd Heinrich, a professor of mine from the University of Vermont, wrote about them extensively in his book “Winter World.” He mused, “Only if I knew how and why a golden-crowned kinglet survives a Maine or Alaskan [or Wisconsin!] winter would I understand the story of winter survival…The kinglet is thus iconic not only of winter, but also of adaptability under adverse conditions.”

I inhaled deeply, a breath of gratitude and wonder at coming across these little miracles of adaptation, but the dry, 11 degree air caught painfully in my lungs. The kinglets showed no such distress despite their acrobatic and aerobic exercise. Not only are their bird lungs quite different from mine, each of their delicate nostrils is covered by a single, tiny feather. I can only lament that I didn’t wear a scarf.

Crunching around to get a better look at the flock, my snowshoes caught awkwardly on twigs and crust. Help as they do, snowshoes can’t quite float my large mammal body on top of the drifts. From my new vantage, though, I got a great look at one of the flock fluttering in mid-air. He could actually hover under the twig to feed, just like a hummingbird. Then with an effortless swoop, he landed on the very tip of a different twig, his two-penny weight barely bending the tree as he dipped his head in continuous feeding motions.

Kinglets need to feed constantly, at almost one peck per second, discovered Bernd. Why this apparent gluttony? In order to maintain their internal furnace at 110 degrees Fahrenheit, kinglets need to eat the 2-to-3 times their own bodyweight of energy dense food each short winter day.

What could kinglets possibly be finding to eat in this barren landscape? Bernd wondered that, too. His research included dissecting a kinglet to examine the gizzard contents—inchworms—then examining the trees themselves to find living examples of those same inchworms, and finally raising the inchworms to adulthood so that they could be identified. The answer: kinglets often eat caterpillars of the one-spotted variant moth (Hypagyrtis unipunctata). These just happen to be relatives of the Bruce spanworm moths I encountered recently, and I can’t help but wonder if the spanworm moths or their eggs might also be food for winter kinglets.

The slight breeze cut through even my puffy winter coat. How are those tiny birds staying warm? Kinglets don’t have a big enough body to store fat like a bear does, but they do grow more feathers each autumn. During the winter, feathers make up 8% of their body weight. Artic explorers wear about the same relative weight of clothing. Just like my jacket, those feathers are great insulation.

But their feet aren’t feathered, I noted, wiggling my warm toes inside wool socks and thick boots. And that is where any desire I might have to be a kinglet stops. Their feet are always cold. It isn’t worth the effort to keep them warm, as long as they aren’t frozen and damaged. The real worry is that cold blood returning to the body from the feet might lower their core temperature. The solution is a counter-current heat exchange system, where arteries with warm blood from the body passively warm up blood from the feet before it re-enters the body.

This evening the kinglets will continue with their constant search for food. They’ll feed until the last instant before dark, then crowd into whatever shelter they can find, and huddle up with the flock. Those are their instructions for life. Amazing, perhaps, but not right for me. I prefer Mary Oliver’s “Instructions for living a life. Pay attention. Be astonished. Tell about it.”  And thanks to the kinglets, I had something to tell you about today.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! The current exhibit, “Nature’s Superheroes—Adventures with Adaptations,” opens in May 2014 and will remain open until March 2015.

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