Shrike!

The heavy snow brought a carnival of birds into our feeders.  Starting at 6:57 a.m., with a black-capped chickadee, there was a steady stream of goldfinches, redpolls, red- and white- breasted nuthatches, blue jays, and even a hairy woodpecker. It was fun to watch as the tiny birds flew in and out of caves in the snow-laden branches of the hemlock trees. Sometimes we could see a little flake of snow stuck to a chickadee’s head, or caught in the whiskers around its bill.

Then, in a flash of feathers, they were gone.

The reason for their quick retreat landed on top of the snow pile. Sporting a black bandit-mask on his gray head, this Northern Shrike looked the part of a feathered villain.

Surprisingly, this skilled predator is a songbird. 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 is 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. Shrikes often kill more prey than is immediately needed and impale the leftovers on long thorns or barbed wire.  Impaling prey on thorns may seem brutal, but it is just a practical way to compensate for having delicate feet that cannot grip food during dinner.

The stored prey also 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. Breeding takes place north of 50 degrees latitude around the globe.  In winter, shrikes migrate only as far as necessary to find food, which often means they come into Wisconsin!  The visitor at my bird feeder should be one his way back home soon, to begin courtship in this month or next.

In the meantime, I hope he is finding enough to eat!  While I love my chickadees, I am an equal-opportunity bird feeder. Anyway, more than half of a shrike’s diet is small rodents like mice and voles.  Unfortunately, those tasty little critters are safely hiding beneath a foot of snow in the subnivean layer. While foxes and owls have enough mass to break through the crust and dig for tunneling mice, shrikes do not have that ability.  Thus, songbirds are a larger part of their diet now, as well as in early spring when male songbirds are distracted by courtship, and in late summer when fledglings are an easy catch. Insects, frogs, toads, and salamanders round out a shrike’s diet.

The carnival of seed-eating songbirds took their sweet time returning to my feeders. They seemed a little more skittish and a little more vigilant as we all scanned the treetops for another glimpse of our thrilling winter visitor.

Turtle Dreams

All winter long, I have been watching the most graceful swimmer. She uses her arms and legs in perfect concert, making subtle motions to move up and down, hang vertically, or even spin quickly through the water. The path of her webbed toes is similar to the sculling motion of a canoe paddle that experienced boaters use for side slipping, or the hand motions of a human treading water. It almost looks as if she is caressing the water. For many long minutes, I get lost in her movements, dreaming of spring ice-out.
 

This aquatic ballerina is Shaun, our pet turtle. She is a red-eared slider, the most common species of pet turtle in the world. Native to the south-central United States, Shaun will be active and highly entertaining all winter, especially when we have extra minnows or worms to feed her. In the wild, red-eared sliders and many other types of turtles hibernate.

Most of Wisconsin’s eleven turtle species spend the winter underwater. This is an amazing feat, since reptiles are air-breathers. Even in the summer, turtles stay underwater for long dives. Winter ice cover simply means an extra-long dive. Because they are cold-blooded, hibernating turtles cool down with the water and have a very low metabolic rate. This lowers their need for oxygen, and with their lack of movement, also reduces the production of lactic acid in their muscles.

Some gas exchange may occur directly through their thick, leathery skin, helping to provide some oxygen and release some waste gases even without breathing. To make absorbing oxygen through their skin most effective, you would think that turtles would try to hibernate in the most oxygen-rich water possible. In fact, map turtles (named for the markings on their shells) do hibernate on the river bottom where fresh water can flow over them.

In contrast, painted turtles bury themselves in the mud. Painted turtles that live in the north are better than southern turtles at surviving long hibernation dives with low oxygen. As acid accumulates in their blood, they buffer the pH by increasing basic cations like magnesium, calcium, and potassium.

Snapping turtles spend winter in a low-oxygen environment similar to painted turtles– under mud in the shallows of small ponds. While the lack of oxygen is stressful, the shallows may warm up faster in spring and reduce the length of their hibernation. As it is, turtles do not feed much when the water temperature is below 65 degrees. Up here, this means that turtles may spend the entire school year hardly feeding if at all!

Turtles have amazing strength and tenacity. For many months, their breathing, movement, and almost all heart activity stops. Then in spring, they resume life where they left off. For 200 million years or so, turtles have done this and prospered with few changes.

 

In many Native American creation myths, the turtle is a central figure. It is told: When the early world was still covered by water, Great Turtle dove deep to bring up mud on his strong back. All the continents grew from that first bit of soil.

Great Turtle’s long dive culminating in the birth of the world is not unlike our present turtles emerging from hibernation into the awakening spring.

Until then, I get to enjoy Shaun’s aquatic ballet while dreaming of summer when her relatives will emerge, and we, too, can swim!

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Mouse Snacks

The light dusting of snow we received the other night was the perfect substrate for mouse tracks.  The morning light revealed a mouse freeway leading from the stack of flower pots to the mess of seed under the bird feeder. Their tiny tracks look like a smaller version of red squirrel tracks.  Mice and squirrels both hop by placing their smaller font feet down first, then bringing their larger hind feet around the sides.  As the hind feet hit the ground in front of the front feet, they give a mighty push for the next hop.  Rabbits also move in a similar way. 
 

You can decipher an interesting bit about the ecology of a hopping track-maker by the placement of their front feet. Arboreal animals, those who spend a lot of time in trees, will place their front feet right next to each other, perpendicular to their line of travel.  Squirrels do this, and a little surprisingly, deer mice are excellent tree climbers and therefore are sometimes paired-front-foot hoppers. Rabbits and hares, who are not often observed in trees, place their front feet with one ahead of the other, at an angle to the direction of travel.  Can you decipher all the tracks in your yard?

The appearance of deer mice – light brown back, white belly, and big ears – is reminiscent of a white-tailed deer.  Mice have much longer tails, though, which aids in their tree climbing.  Deer mice have a closely-related and almost indistinguishable cousin, the white-footed mouse.  To tell them apart, experts look at a difference in the amylase molecules of their saliva.  You might remember amylase from biology class when you chewed on crackers until they tasted sweet.  Amylase is an enzyme that breaks carbohydrates into simple sugars.

 

Food is especially important during the winter for these tiny active critters.  Mice will cache food (including weed seeds, birdseed, berries, and my cookie crumbs) in the fall, and throughout the winter.  Several times I have curiously brushed the snow off of an abandoned bird nest and discovered a tidy little mouse pantry.  Earlier this winter I accidentally left a Mason jar with birdseed in it on the patio.  I found it a few days later, with the contents spilled onto the snowy path.  Squirrel tracks, mouse tracks and tunnels surround the windfall as they busily hoarded the treat.

Eating plenty allows the mice to run their metabolism on full speed to keep warm.  In the winter they add new red blood cells with more hemoglobin to fuel their roaring metabolism. After creating all that heat, mice do their best to conserve it through the day when they are not active.  Body temperatures may be allowed to drop as they snuggle in next to other mice in a cozy woodpecker hole, thatched-grass nest, bluebird box, or the warm micro-climates of our homes.

Peering out of my home early one morning, I witnessed a bit of natural drama.  My local gray fox stood on the path by the corner, in person, not just in tracks! He was just ten feet away, standing over the remnants of spilled birdseed.  In the shadowy pre-dawn, I watched as he nuzzled the snow and came up with a limp mouse hanging from his jaws.  With a flick of his head, the mouse disappeared in one gulp. The fox trotted nonchalantly down the path leaving delicate tracks in the fresh dusting of snow.

In December, the fox tracks whispered “Listen…it is music to run over the hills” Now he adds: “Death itself is a music…It is flesh and bones changing shape and with good cause. Mercy is a little child beside such an invention.” (Straight Talk from Fox in Red Bird by Mary Oliver). 

 

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Love is in the Air

It's mid-February, near Valentine's Day, and love is in the air. Literally. Many animals are anticipating or are in the midst of their breeding seasons right now, and they are advertising it through air with sound and scent. You've probably heard a few eager chickadees singing their "hey sweetie" love songs despite below-zero temps. They won't breed until April, but it doesn't hurt to get a head start impressing the ladies, right?

If you have owls near your home you may be hearing their eerie calls more often. Great horned owls and barred owls both mate this time of year, and are calling back and forth to communicate both with potential mates and potential competitors. One of the great horned owls' prey species, the wild turkey, has also been noticed strutting to impress the ladies recently.

Wolves have already been thinking amorous thoughts for a month or so. You may have heard them howling along with the owls. Within a pack, typically only the top male and the top female (the alpha pair) mate. They will announce their intentions with a "paired RLU." This is where the male initiates raised leg urination (RLU) to leave a scent mark, and the female then urinates next to his. If the female is in estrus, you may see a few drops of blood on the snow.

Bobcats are typically a solitary species, but this time of year the males and females will strike a tentative truce for mating season. Males and females will increase their scent marking behavior, which may help them learn about potential mates, and find each other when the time is right.

Two of the bobcats' favorite prey species, gray squirrels and red squirrels, are also starting to feel amorous. You may have noticed that the squirrels have been extremely active recently. Their mating rituals begin with a chase, as up to ten males compete for one female. Their arboreal acrobatics can be quite entertaining. Male squirrels can smell when a female is in estrus and ready to mate. This is a useful skill, since she is only fertile for one day.

Often in mid-winter I will notice little splotches of red in the squirrel tracks around my bird feeder. I haven't been able to find any information relating directly to this, but my guess is that it's a sign that a female is in proestrus, and, just like the wolf, is leaking a little blood. As spring keeps peeking at us from around the corner, we will continue to see even more amorous behavior in the woods.

What are your plans for Valentine's Day? Perhaps you will consider wooing your date with a sweet song or a designer perfume!

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Ode to the Glaciers

What do you love most about Northern Wisconsin? Rolling hills traversed by some of the best trails in the country, winding back roads, sparkling lakes, and shady green forests are some of my favorite features. Have you ever wondered why all these wonderful things come together in Northern Wisconsin? Maybe you know that this region was shaped by glaciers, but have you ever really sat down and appreciated all that the glaciers did for us?

I love glaciers. I have never seen one in person, and yet they have vastly improved my quality of life. Whether you realize it or not, you also know the joys of glaciers whenever you whiz down a rolling ski trail, hike merrily up and down hills, enjoy the stomach-dropping exhilaration of catching air on your snowmobile, or boat and fish on one of Wisconsin’s more than 10,000 lakes.

The landscape around Cable and Hayward was shaped during the Wisconsin Glaciation (named for us!) of the Quaternary Ice Age (which is still going on in Greenland and Antarctica). It began about 100,000 years ago, hit its maximum extent about 21,000 years ago, and the last glacier had retreated out of Wisconsin into Canada by 10,000 years ago.

The very recent (geologically speaking) visit of a glacier here has had a profound impact on what the landscape looks like. As glaciers advanced across the land they scraped and carved and plucked up rocks from their path, and carried them along within the ice mass. Like a conveyor belt, they brought tons (literally) of sediment south with them. Two lobes of ice flowed into our area, and their lateral margins met somewhere near Cable.

Where we really start to get interested is when the climate warmed and the ice began to melt faster here at its toe than new snow from Canada could replenish it.  Huge chunks of ice were left behind from the melting edges of the glacier, and then glacial outwash rivers carrying meltwater and debris off the glacier buried those ice cubes.  Well-insulated, the ice lay hidden under a flat surface of sand, gravel and cobbles for many years.

As the ice melted, basins of all shapes and sizes were left behind where the ice had been. Sometimes these basins, called kettles, filled with water and became lakes, others are perched far above the water table and stay bone-dry. The landscape of sandy, rocky soil pockmarked by kettles is called a “pitted outwash plain.” The Rock Lake ski and mountain bike trails east of Cable are a prime example of this topography, and in my opinion, a prime place for recreation because of it. The Birkie Trail takes advantage of the varied topography so much that its hills are legendary.

In places, the glacial conveyor belt stagnated for a while, leaving a line of jumbled sediment where its margin had been.  This is probably what created the wacky shoreline of Lake Namakagon – with many shallow bays and great fish habitat.

Even the towering spectacle of Mount Telemark owes its existence to the glaciers – rivers flowing on top of the melting ice carried rocks into a large crevasse.  When the glacier melted, a 1,700-foot-tall pile of sand called a “kame” was left behind. It is the tallest kame in Wisconsin.

Not only did the glaciers shape the physical landscape, they, by extension, continue to impact the human uses of it.  Unlike regions to the south and north, we don’t have extensive farming.  Not only are there too many hills, but the soil just keeps growing more rocks. First, water to percolates underneath buried rocks. When it freezes, the ice crystals lift up the bigger rocks and sand falls underneath. Over many freeze-thaw cycles, the rocks come to surface, right in your carrot patch! Happily, many trees grow just fine in this type of soil, so our local crops are forests instead of corn.

The next time you’re out for a spin on a lake, road or trail in Northern Wisconsin, take a moment to appreciate the wonderful legacy of the glaciers.

Subnivean Chronicles

Adventures in the woods lately have revealed fewer species than earlier in the winter. Have you noticed a change? Tracking stories these days are mostly written by little feet, and many of the stories lay hidden below the surface. Now that we actually have a thickness of snow on the ground, a new world develops beneath our feet. This ephemeral habitat is called the Subnivean layer. Since I first learned about this hidden zone as a bright-eyed college freshman, it has taken on a mythical quality in my imagination. Subnivean sounds like it could be a region of Narnia ruled by the White Witch, or perhaps an outpost neighboring Rivendell in Middle-earth.

The Subnivean layer, like so much of life on Earth, owes its existence to the unique chemistry of water. When frozen, water becomes light an airy, a wonderful insulator. Just as down feathers in your jacket trap a layer of air next to your body, retaining the heat you radiate, a six-inch layer of snow traps air that retains heat from the Earth. We don’t have hot-rock geothermal here, no geysers or hot springs. Our ground warmth, used in many local geothermal heating and cooling systems, comes not from radioactive decay in the Earth’s core, but simply from sunlight absorbed into the upper layers of soil and stone.

Because of this insulation and radiating heat, a thin zone opens up under the snow, right at the surface of the ground. As water freezes, it releases a tiny bit of heat, and as it melts, it absorbs a tiny bit of heat. In this way, the temperature in the Subnivean zone is regulated at a pretty stable 32 degrees Fahrenheit. Compared to -20 with a 15mph wind at the surface, that feels pretty balmy!

Many tracks are now being pressed invisibly into the leaf litter that carpets the Subnivean layer. Shrews, voles and mice, small mammals depend on this habitat for food, warmth, and protection from predators. Their presence is betrayed where the tiny jumping tracks of a deer mouse connect small trees with fallen logs. The tunnel of a shrew will suddenly exit the snow at the edge of a ski trail or where snowshoes have packed down a trough. The impossibly small holes can be not much wider than ½ inch. Sometimes shrews and voles will tunnel through the surface of the snow, especially the fluffy stuff, leaving a winding trough that ends in another hole when they again descend into the fabled Subnivean layer.

Although soft and concealing snow may seem like a perfect security blanket, the fat and juicy prey are not safe from their wily and well-adapted predators. Owls can hear mice through the snowpack, triangulate the sound with their asymmetrical ears, and bust through the crust with fisted talons. Foxes and coyotes can also hear and pounce through the crust, thus securing a meal without even seeing it. Our three smallest weasel species – long-tailed, short-tailed and least, are long and skinny with short legs for a reason. They can snake their way through mouse and chipmunk tunnels to catch the critters right in their own dens. Then the weasel will feast and nap at the warm hearth of its meal before going out to eagerly search every tree, log, rock and stump for another tasty treat.

You may also have noticed the prolific squirrel tracks, connecting trees to small holes littered with leaf shards and pine cone scales. Red squirrels will tunnel to find food caches stored last fall, and often put a big hole in the ski track in the process.

Grouse also make use of the warm blanket that snow provides. When the snow is deep enough, they may “roost” by doing a swan dive, leaving no tracks that would lead a predator to their warm bed. In bad weather, a grouse may stay in its burrow for a few days. Back-country skiers and snowshoers tell stories of grouse flushing from these secret burrows just inches in front of their next step.

While many tracking stories are hidden these days, it’s fun to imagine the complex chronicles unfolding in the Subnivean world. What lies beneath the smooth white surface? More than we will ever know.

Seeing Things

As I came around the corner, a dark blob at the edge of the road caught my eye.  You know how we are always seeing things that aren’t there?  Mailbox reflectors turn into deer’s eyes in our headlights. Tall stumps look like black bears.  Clumps of leaves take on the shape of an owl.  The dark blob was less than three feet tall.  It had pointy ears and a sloped back.  It was black against the bright mid-day sunlight and white snow.  Then, in an impossible moment, it went leaping back into the tangled fir thicket.

Bobcats aren’t rare in Wisconsin, but I’ve only found one set of their tracks in all the miles of trails I’ve hiked and skied in Wisconsin.  Actually seeing an animal make tracks is an excellent learning opportunity, so of course I stopped the car in an open stretch of road, put on the blinkers, and went over to check out the disturbed snow.  Since the flakes were light and fluffy, none of the four toes were visible in the tracks.  I could tell generally where the wild feline had walked calmly up to the edge of the road, sat down for a bit, and then hurried off with big poufy bounds. 

If I hadn’t seen the actual cat, I don’t think I could have identified its tracks.  I could tell, by the size of the body and size of the tracks, that this was not a lynx.  Canada Lynx, with their four-inch wide, snowshoe-like feet, have never been abundant in Wisconsin, since they prefer the deep snow and thick conifer habitat of their favorite prey—snowshoe hares.  Some years, when the snowshoe hare population in Canada crashes, lynx will wander down to Wisconsin to find food.  There hasn’t been a sighting in Wisconsin since 1992, and only 28 verified records since 1870.  Because lynx are so rare here, they are listed as a Protected Wild Animal, but not as a State Endangered Species.  They are on the federal list.  Bobcats can be trapped and hunted.

A few weeks ago in Minnesota’s Cascade River State Park, I watched as a bobcat walked up the trail toward me. It chose a soft place in the pine needles and laid down for a catnap, or perhaps it was waiting in ambush for a squirrel.  Some minutes later it stood and stretched.  Maybe it wasn’t hunting as much as digesting, since it paused then to squat and deposit a long, dark hair-filled scat.  With that business taken care of, it walked daintily down the trail.  A string of oval tracks just smaller than my lip balm were pressed into the light dusting of snow.

Don’t you believe me?  I watched it happen, just like a movie, in my mind’s eye.  The body print was just so on the pine needles, the four tracks of a squatting position had an extra sharpness due to added pressure and time.  The scat was positioned exactly where you’d expect it to be.  Poet Mary Oliver tells a similar tale from deer tracks in The Pine Woods, and challenges us, saying “But I don't believe only to the edge of what my eyes actually see in the kindness of the morning, do you?” 

Was I seeing things?  Absolutely, and that is the very essence of tracking.