Friday, April 25, 2014

Turkey Vultures

What signs of spring have you spotted lately? About a month ago, my dad reported seeing his first turkey vulture of the year down in Iowa. Most people probably don’t associate these drab, brownish-black scavengers with spring--or even realize that vultures may have flown as far as South America for the winter--but they are one of the earliest returning migrants. “What blazes the trail,” writes Mary Oliver, “is not necessarily pretty.”

Sure enough, a few weeks after Dad’s report, I caught sight of the V-shaped wings and rocking, unsteady flight of a turkey vulture soaring above my road. I suppose the “buzzard” had to wait until temperatures increased enough for warm-air thermals to rise and buoy up its gray-fingered wings.

For as long as I can remember, Dad has been pointing out every turkey vulture (TVs he called them) soaring over every road trip we ever took. And it was fun, even as a kid, to be able to easily identify such a large bird flying so high up in the sky. They have an excellent gross-factor, too, which kids love. “Don’t get to close to a turkey vulture,” warned the park ranger on my first grade field trip to Effigy Mounds National Monument, “they’ll throw up all over you!” That I still clearly remember this fact, and the moment I learned it, is an excellent argument for outdoor education.

Since that day, I’ve discovered many more gross facts about turkey vultures. First of all, projectile vomiting is a defense they use against predators, not just curious humans. The foul-smelling mix of semi-digested meat and digestive fluids can sting if it reaches the predator’s eyes. In addition, emptying their stomach may be necessary to lighten the load for take-off and escape if a TV is interrupted while gorging on a roadside carcass.

Turkey vultures don’t just spray gross stuff on enemies; they also defecate on their own legs. This habit has a scientific name (urohidrosis) and a valid purpose. As water evaporates from the combination of urine and feces (birds don’t separate their waste like we do) it cools the blood vessels in their legs and feet. It’s quite handy, actually, if you can’t sweat.

Even without sweating, vultures’ feathers sometimes become damp during dewy, foggy, or rainy nights. Then, while they wait for the air to warm enough to begin rising in thermals, TVs perch in a spread-winged stance in the sunshine. This not only dries feathers, but it warms their body, and bakes off bacteria.

Not everyone sees vultures as gross. Tibetan Buddhists practice “sky burials,” where vultures consume the dead, and Buddhists respect the birds for their role in cleansing the earth and continuing the food chain.

While their diet of rotting meat may repulse us, turkey vultures dispose of carcasses that could otherwise breed disease. Can you imagine a world in which dead things all rotted slowly in place? Turkey vultures embody the fact that “the secret name of every death is life again.” (Mary Oliver, Skunk Cabbage)

In response to their diet, TVs have developed excellent immune systems that can ward off and even destroy the microbes that cause botulism, anthrax, cholera, and salmonella. Their stomachs, gross as they may seem, help purify our world.

Indeed, despite their gross appearance, every adaptation of the turkey vulture seems aimed at cleanliness and purification. Even their bare, ugly heads serve to keep turkey vultures clean. While they are feeding on those carcasses, TVs sometimes need to stick their heads deep into the cavities of the dead animals. They preen the rest of their body feathers frequently, but can’t clean their own head. The lack of feathers allows sunlight to sterilize their skin.

While we don’t usually think of urine as cleansing, turkey vulture urine helps to kill bacteria they might have acquired while walking over a dead animal.

So although they may appear gross, TVs’ scientific name -- Cathartes aura—is quite appropriate. It means “purifying breeze.”

And in fact, the story of the vultures – of winter’s rotting wounds transformed and purified, of the purifier rising up into the sky, of it returning to cleanse the world again and again—sounds a lot like another story I often hear this time of year.

“Like large dark lazy butterflies they sweep over the glades looking for death, to eat it, to make it vanish, to make of it the miracle: resurrection...” from Vultures by 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, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.

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


Monday, April 14, 2014

The Excitement of Spring

Spring is a season of change. All around me, things are changing color, new structures are being built, and a fresh cacophony of sounds fills the air. And that’s just inside the Museum! April is our exhibit construction month. Staff and volunteers demolished (and recycled) our old exhibit in just a few hours. Now the saws are humming, the cordless drills are whining, the carpenters are joking, and the paintbrushes are swishing.

A rainbow of geometric shapes grew to cover our dark green walls. Display boxes of all sizes and shapes, with hidden shelves for video equipment and holes for buttons and cords, seemed to spring up right out of the floor. A flat board metamorphosed into a flying superhero sidekick under the skilled brush of a volunteer artist.

Outside, a similar transformation is taking place. Bright sunshine and warm winds deconstruct winter’s snowdrifts. Eagles and osprey return as the rivers and lakes open up, and they gather sticks to refurbish old nests and construct new ones. Spiders are coming out of hiding to weave their webs, and some insects, suspended in a juvenile form all winter, will soon start metamorphosing into adults.

One color change I’ve noticed is the browning of hemlock needles in my yard. I’ve also noticed discolored evergreen trees along highways. Those I know are from salt spray off the roads. Passing cars splashed up salty water all winter. The evergreen needles absorbed some of the salty liquid. Once enough salt accumulated, it became toxic, and the needles died back from the tips.

I was a little more surprised at the trees in my yard turning brown, since they are not near any road. Serendipitously, a few days after I noticed my browning hemlocks, the Minnesota DNR published an explanation: strong, dry winds, many days of bright sunshine, and low relative humidity all contribute to the needles drying out so much that they die. It is possible I only noticed the damage recently because we’ve only had extended periods of strong sunshine recently.

Happily, the buds protecting new growth on trees are extremely tough, and tend not to experience winterkill. Even on the trees damaged by toxic road salt, new shoots will develop after spring rains wash the salt away.

So goes spring at the Museum, too!

Soon we will forget our winter-dried skin, our season with little color, our spirits that withered during the last (last!?) blizzard. Just about the time that frogs start peeping from the wetlands and warblers start chatting in the woods, first graders will start peeping in the classroom and visitors will be chatting in the exhibit. Come share the excitement of spring with us and our new exhibit—Nature’s Superheroes: Adventures with Adaptations—that opens May 1st!

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.

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


The balance of fire and ice

The morning stretched on like a cat basking in the sun. Freshly groomed ski tracks led us on a winding journey through golden-barked poplar stands, dense fir thickets, and across sunny meadows of windswept drifts. Wolf tracks, perfectly imprinted onto the smooth ski grooves, trotted along with us. Fox tracks floated across the icy crust; a remnant of last night’s mischief.

We seemed to glide on the boundary between fire and ice. The sunshine toasted our cheeks, foreheads, and tender necks to a crispy shade of red. Our skis swished along on icy snow, carrying our bodies through a dynamic temperature range.

Early spring is a time of shifting balance. The ice, which had been winning the battle for months, finally starts to weaken in the face of an intensifying sun. It is an age-old contest. The early stages of this fight make for absolutely fantastic spring skiing and snowshoeing. Warm sun for your face meets slick and supportive snow for your feet. The scenery isn’t half-bad either, when bluebird skies provide the backdrop for snow-dusted branches and clean white hills.

As the sun dipped low, more magic shimmered through. Glassy jumbles of ice panes on Lake Superior’s rocky north shore captured the last rays of light.  Out in the widening pools of open water, newly broken shards moved against one another in a gentle, tinkling, watery symphony.

By the next morning, the sun had redoubled its attack, and the ski trail softened in retreat. The glorious warmth on my face soon eclipsed the fading quality of the ski trails as a source of pleasure. I changed boots, and changed surfaces. Then, as a strip of wet blacktop road led me winding through hardwoods, the air held the scents of damp wood, wet leaves, and fresh life. Actually, the whole forest smelled like maple syrup.

It doesn’t matter that I woke up to an ice-encrusted car, or that another inch of snow fell throughout the day. It doesn’t even matter that yet another blizzard is hissing through the woods as I write this. The ice is on its way out. It may win another battle or two, but the sun will win the war.

“…Do you think there is anywhere, in any language, a word billowing enough for the pleasure that fills you, as the sun reaches out, as it warms you…?” –Mary Oliver, The Sun

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.

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


The Black-Masked Bandit


Let me take you back again to the sunny forest at the North End Trails near Cable, WI. A colorful line of thirty students, several parents, and a couple of teachers – all on snowshoes purchased with a grant from the Wisconsin Environmental Education Board – stretched out behind me on the trail.

The students could sense that the hike was almost over, and I’d already reassured some that it was all downhill from here. I was looking ahead to my next stop at the fox station, and eavesdropping on the students’ excited conversations behind me, when a teacher called out, “Hey, Miss Emily, there’s a dead mouse in this tree!”

Well, that stopped me in my tracks. “Are you serious!?” I called back, nearly bursting with excitement. “That’s awesome!” I stepped out around the students and started tromping through the deep snow back to where she stood. I waved to the kids in the front of the line to turn around and walk back with me.

There, nestled in the delicate fork of two sugar maple twigs, just above my eye level, was a very dead mouse. “That’s awesome!” I said again, probably striking fear into the hearts of the parents who were wondering how someone this weird came to be leading their children through the woods.

And then I started to explain: this mouse was most likely stored here by a bird called a Northern Shrike. When shrikes are able to catch more food than they need in a day, they store it for later use. Sometimes they’ll impale prey on thorns, or barbed wire fences. When those aren’t available, the fork in a twig will do.

Stored prey provides the shrike with food security, and will eventually get eaten when the hunting is poor. A male shrike with abundant prey impaled throughout his territory has a better chance of attracting mates and fathering successful nests, but this bird probably wasn’t worried about attracting mates. Breeding takes place north of 50 degrees latitude around the globe (that’s northern Canada). In winter, shrikes migrate only as far as necessary to find food, which often means they come to Wisconsin!

Surprisingly, these skilled predators are songbirds. Being songbirds, shrikes lack the sharp talons of raptors like hawks and owls. Being songbirds, shrikes have another weapon. Like the winged Sirens of Greek mythology, shrikes sing sweetly to attract other songbirds.

Once prey are lured in, shrikes attack with a solid blow, then finish the job by biting the neck, shaking, or repeated knocks to the skull with their sharp beak. Impaling prey on thorns or sticking them in forked twigs may seem brutal, but it is also a practical way to compensate for having delicate songbird feet that cannot grip food during dinner.
Sporting a black bandit-mask on their gray heads, Northern Shrikes look the part of a feathered villain.

More than half of a shrike’s diet is small rodents like mice and voles. Right now, most of those tasty little critters are safely hiding beneath a foot of snow in the subnivean layer. This unlucky mouse must have been caught running on top of the snow, above the relative safety of the subnivean zone. While foxes and owls have enough mass to break through the crust and dig for tunneling mice, shrikes do not have that ability.

We hadn’t seen a single mouse track on the snow in our two days of field trips, so this mouse might have been caught and stored a few days ago, before the last storm. It certainly looked a tad dehydrated.

After snapping a couple photos, I snowshoed back to the head of the line and kept the group moving. I’m not sure what those kids (or teachers and parents) thought of our discovery. A gross oddity? A cool animal sign? A scientific curiosity? In any case, the naturalist in me is thrilled to find evidence that a shrike is visiting our woods. I’m not the least bit sad that there is one less mouse running around, especially since it came to such an educational end.

“…And you know theirs is a decent task in the scheme of things – the hunters, the rapacious plucking up the timid like so many soft jewels. They are what keeps everything enough, but not too many…” –Mary Oliver from Bowing to the Empress.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.

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