A Natural History of Thanksgiving Dinner

The Thanksgiving dinner menu is often pretty standard. When you’re feeding a large group of people with picky kids (and adults) to satisfy, and traditions to uphold, it doesn’t pay to get crazy. You can’t go wrong with  turkey, green beans, potatoes, cranberry sauce, and pumpkin. But have you ever thought about what those foods are like before they get to your table? You may have given thanks for the bounty, and perhaps even for the Earth that provided them. But do you think about how and where they’ve grown in the dirt, under the hot sun, for thousands of years? Or  the odd adaptations that keep them alive? Maybe  your “normal” Thanksgiving dinner is pretty extraordinary.

Let’s start at the end, with pumpkin pie. If you’re ambitious, you may have  baked a pumpkin and scooped the soft, orange flesh out of the rind. Although I enjoy pumpkin pie, I’ve often thought it a little weird to take a vegetable, mix it with sugar and eggs, and make a dessert. Personally, I prefer a berry pie.

But, to  a botanist, a pumpkin is a berry! Scientifically speaking, a berry is a fleshy fruit produced from a single flower. Pumpkins are a  type of thick-walled berry known as a pepo. Appropriately, the scientific name for the pumpkin is Cucurbita pepo. C. pepo is also the name for the acorn squash, delicata squash, spaghetti squash, pattypan squash, zucchini, and ornamental gourds. Despite the fact that some on the list are hard-skinned winter squash, and some are soft and juicy summer squash, they are all fruits of the same species of plant.

That plant was domesticated from its wild ancestors about 10,000 years ago. We know this from the large seeds—characteristic of C. pepo, but not it wild cousins—that were unearthed in a cave in Oaxaca, Mexico, and dated using carbon-14. That makes pumpkins and their cousins the oldest known domesticated plants in the Americas.

While the beans in your green bean casserole aren’t quite that old, they are one of the longest-cultivated plants in the Americas. Kidney, black, pinto, and navy beans all were domesticated in South America. As with pumpkins, many types of beans all belong to the same species: Phaseolus vulgaris (vulgaris means common). Green beans are simply the unripe fruit of various cultivars of the common bean -- selected especially for the fleshiness, flavor, or sweetness of their pods.

Long before humans domesticated beans, the beans developed their own beneficial relationship with another organism. Through a series of chemical signals, soil bacteria called rhizobia trigger the bean plant to grow deformed root hairs that expand into nodules. The bacteria waltz on in, becoming guests in the bean plant’s spare room. While the bean feeds the rhizobia with carbohydrates, proteins, and even oxygen, rhizobia are not moochers. The bacteria possess the rare talent of taking nitrogen out of the air, and fixing it into a form that the beans can use.

This special relationship between the beans and the bacteria impacts our relationship with beans, too. Nitrogen is a basic building block of amino acids, and amino acids are the basic building blocks for protein. The mutualistic symbiosis that beans have with rhizobia give the beans the high protein content we desire.

The bean plants themselves also make pretty good houseguests. Microscopic hairs on their leaves can be used to trap bedbugs!

Leaves from the potato plant are also bad for bugs. All parts of the potato plant – except for the tuber itself – contain toxic alkaloids like solanine that are supposed to protect the plant from its predators.

Human predators–hunters--are one of the biggest causes of mortality for the Thanksgiving centerpiece. Hunters are responsible for two thirds of the mortality in tom turkeys. Of course, you probably weren’t eating a wild turkey. But if you were, could you have figured out how good his genes were, and if he had intestinal parasites or not? The hens could have!

Turns out, it’s all in the snood. This fleshy outgrowth hangs down over the male’s beak and is used to dissipate heat when he’s strutting his stuff. A longer snood also signals to the ladies that he has good genes that are helping him ward off intestinal parasites. What a life!

All of the dishes on our Thanksgiving table were made from living things. But before they went into the pot, they had lives filled with history, drama, stress, and relationships not so unlike ours. And now, their lives are part of ours, sustaining us with vital products created in their very own bodies. “How calmly, as though it were an ordinary thing, we eat the blessed earth.” -- Mary Oliver.

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.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

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.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Passenger Pigeons and Lyme

Today my roof is buried under more than a foot of snow, and the drift is sliding off of the high-angle metal in a slow-motion avalanche. Not long ago, my roof hosted an avalanche of a very different kind – an avalanche of acorns.

Back in August, I started hearing weird noises on the roof. A loud plunk would be followed by a series of rattles, then silence, and sometimes a final plink. While working in the garden one afternoon, I figured it out. The noises started, the short silence ensued, and an acorn launched off the roof, sailed over my head and plinked on the roof of my car. Every slight breeze brought the same series of events hailing down on me from the large oak in the yard. The driveway soon became a roly-poly mess of round, brown nuts.

Oaks are mast trees, which means that they save up their energy for three to five years before producing thousands of acorns all at once. And single trees don’t usually mast on their own. Somehow, all the trees in an area communicate to determine which year will be the right one. “In the old time, our elders say, the trees talked to each other,” writes Robin Wall Kimmerer in her book Braiding Sweetgrass.

Scientists don’t go for that explanation. Foresters hypothesize that trees simply wait until they’ve built up enough energy. But that doesn’t explain how trees in rich and poor habitats are ready at the same time. Mycologists now theorize that the networks of mycorrhizal fungi that connect a forest by the roots may be the agent of coordination. “A kind of Robin Hood,” writes Kimmerer, “they take from the rich and give to the poor, so that all the trees arrive at the same carbon surplus at the same time…Through unity, survival. All flourishing is mutual.”

Why does masting together equal flourishing? It is simple math. With thousands of acorns available at once, the hordes of acorn-eating seed predators cannot possibly eat them all. Some, at least, will survive to grow a new tree.

At least, that is how it works today. In the past, there was a seed predator that could clean out an oak forest, even in a mast year. Passenger pigeons, once the most numerous land bird on the continent, traveled in flocks of millions. When they descended on a grove of oaks, the twigs, branches, and even whole trees broke under the weight of their bodies. By one report, not an acorn could be found after they moved on.

Their nesting colonies, by necessity, also followed the mast. The largest nesting area ever recorded was in central Wisconsin in 1871. The size was estimated at 850 square miles. The population was estimated at 136,000,000 birds. It takes a lot of food to support that many birds, even for the two months or less it took to mate, brood, and fledge the squabs.

Now that passenger pigeons are extinct (the last one died 100 years ago this fall), it’s difficult to tease out the significance of their lives, and the consequences of their demise.

What we do know is the impact that extra acorns (presumably the ones no longer eaten by flocks of pigeons) have on several other species. In New York, scientists have shown that Lyme disease increases two years after an acorn mast year. The mechanism seems to be the increase in white-tailed deer numbers and local density, along with an increase in the population of mice (one of the best carriers of the Lyme-causing bacterium).

Deer help the ticks reproduce. Mice infect the ticks with Lyme disease. The ticks infect us. If the pigeons were still here to eat all the nuts, and prevent the local concentrations of deer, mice, and infected ticks, hypothesizes ornithologist David Blockstein, would that also keep the spread of Lyme disease in check?

The world is a complicated place, and we can never fully predict the consequences of our actions. None of the nineteenth century market hunters--who slaughtered thousands of passenger pigeons per day with the conviction that they would always be plentiful—would have ever suspected that their actions might result in their descendants suffering from a tick-borne disease.

Jerry Niemi, from the Natural Resources Research Institute, at the University of Minnesota, Duluth, recently spoke on the rise and fall of bird populations in Minnesota and Wisconsin. Since the year 1600, he recounted, 131 species of birds have become extinct. Today, another 1213 species are facing the threat of extinction. That is 12% of all known species of birds. What cascade of events will their losses trigger? What kind of avalanche will climate change bring? Certainly not one as quaint and harmless as acorns or snow tumbling off my roof.

Kimmerer’s wisdom sums it up for me: “What happens to one, happens to us all. We can starve together or feast together. All flourishing is mutual.”

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.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.

Five things that improve after a hard freeze:

1. Sparkling rubies nestle in emerald green moss, illuminated by the weak glow of a headlamp. Dampness oozes from the deep layers of peat soil, and from the fresh layers of sphagnum that climb the scaffolding of twiggy leatherleaf bushes. And my boots. The dampness also oozes around my boots.

Reaching, stretching, I search almost manically for the little bog jewels. Ignoring back aches, ignoring the way that damp moss and damp breeze suck the warmth from fingertips, ignoring a friend who is not ignoring those things and wants to go home. The one quart yogurt tub in my left hand has almost been filled with cranberries by my right hand. Almost. Not quite, and look, there’s another patch by that hummock.  And another over there. That one is pale and firm--not yet frosted and sweetened. Look! Three perfect jewels dangle among dry threads of grass.

The first (or second?) wet snowstorm of fall had pushed marble-size berries deep into the moss. Then it melted. More snow is forecast, so we must pick everything we want now, under the cloudy darkness, listening to the rush of city traffic not far beyond the soggy bog and tangled forest.

A cherry red gem gleams from its cozy bed. I pluck it with numb fingers; listen to it plunk onto its comrades. In its hole, I spy more red. I scoop that one up too, only to see a third fruit shining from even deeper. This one is so perfectly ripe that I place it on my tongue, gently pressing it against the roof of my mouth until it bursts. No one sees my pucker face in the dark. Nor do they hear the involuntary hum of satisfaction as the frost-softened, cold-sweetened, pungently wild flavor of the bog fills my night.

2. The hard edge of my library card peels elegant curls of frost off the windshield. A quick peek under the garden cold frame reveals a small grove of deep green spinach–frozen solid. Oh well; next year I’ll eat them sooner. But hard frosts require a clear sky, and the day soon warms. Later, I find my spinach cheerful, thawed, sprightly and intact. Into the salad bowl, quick, before it’s too late! Unlike the wilted and bitter salads of summer, these leaves are sturdy and sweet, requiring much grateful mastication in my sunny kitchen.

3. A friend tells me that his delivery guy drove through a sideways storm. It’s gone now, but the northwest sides of the tree trunks are white—skunk striped with damp, driven flakes. Our hiking boots make sculpted designs in the snow. The woods are silent and still. We see only red squirrels and one hairy woodpecker. But others have been here recently. Otters, fishers, foxes, voles, and shrews crossed our path. The snow holds the record of their presence and their passing. Otherwise, how would I know? Snow makes the forest feel alive.

4. In the sunny opening created by a fallen sugar maple, little tan moths flutter feebly. Moths? But it can’t be more than forty degrees. Quick! Get a photo! Here, I caught one. Delicate fringes outline their wings, while darker brown, fuzzy, scalloped lines fill them in. They are everywhere. On the snow. Deeper in the woods. Drifting in front of our noses.

Bruce spanworms are pesky little green and yellow inchworms that turn unfurling spring leaves into lacy green skeletons. They prefer sugar maple, aspen, elm, and apple. In June, they pupate, and wait until cold drives away hungry bats, birds, and predacious insects. In the relative safety of the late-fall woods, the adults emerge. Wingless females, full of eggs instead of flight muscles, simply crawl up the nearest tree to waft pheromones into the breeze. They wait. Meanwhile, the males give thanks for antifreeze, and shiver large flight muscles up to temperature. The cold dictates relatively slow wing beats, but those wings are broad enough to carry a lightweight body through the air. Females lay pale green eggs into the grooves of bark. Neither adult eats. Over winter, the eggs turn orange. Unfazed by the cold, the caterpillars hatch in May.

5. Mosquitoes. My deepest gratitude to whichever source of infinite wisdom reserved the power of winter flight for soft-winged moths, and not mosquitoes. Praise be to the hard freeze. Praise be to the delicacy of their little, buzzing lives.