Dust From a Distant Sun

Aurora Borealis by Heather HinamAutumn has flown by, marked by brilliant leaves and skies filled with birds winging their way to warmer climes. The bustle of the season swept me up with back to school (I haven’t taught a fall course in over 7 years) and my regular work as a naturalist/guide/illustrator, leaving this blog sitting on the shelf for a while.

However, now, as the nights turn truly cold and the days become darker, I finally have a chance to settle and get back to sharing those things that fascinate me the most. I thank you for sticking with me.

The colder temperatures remind me of the many reasons I love living in the more northerly reaches of the planet. Not the least of those is the chance we get, now and then, to witness one of the most amazing natural phenomena on earth: the auroras. Here, in the northern hemisphere, they are the aurora borealis or northern lights. They’re not actually more common in the colder months; but many tend to associate them with winter, probably because the longer nights give us more opportunity to see them.  The picture above was actually taken in August.

For people who have never seen them, aurora are kind of hard to describe. They appear with no warning, beginning usually with a barely noticeable glow just above the horizon. You stare, transfixed, wondering if you’re seeing things. Suddenly, the silent flames grow, licking out across the sky, a rippling curtain of light that is ceaseless in its movements. The shifting colours hold you in their thrall until, just as quickly as they had appeared, the lights dissolve into the ether, leaving you feeling a little bereft for their loss.

Just what are these silent, shimmering waves of light? Though they are best seen on the darkest of nights, aurora are a product of the sun. Being a giant ball of hot plasma (ionized gas particles), the sun is a tempestuous place to be. Protons and electrons are being flung about the atmosphere, creating ‘solar winds’, which are streams of plasma that escape the star’s gravity and sail across the universe at truly mind-boggling speeds of millions of kilometres per hour. On occasion, fountains of particles will spew out of the sun’s atmosphere in a coronal mass ejection, sending a wave of protons and electrons on a collision course for earth.

When they reach our magnetic field, most are deflected, riding the field lines to the poles, where they start to swirl around, like atomic tornadoes, in the ionosphere (the height at which the International Space Station orbits). Whirling faster and faster, the ions become unstable, colliding with nearby gas atoms, releasing so much energy that they glow. The colour of the light depends on the gas they interact with and how far above the earth they are. The green and yellow we are most familiar with is created by an interaction with oxygen, while blue and violet are caused by nitrogen.

So, what you’re seeing is millions of chemical reactions playing out several hundred kilometres above the earth. The unearthly flame is concentrated in a halo around each pole, an auroral ring that shifts ever so slowly with the movement of our magnetic poles.

For the layperson, the appearance of these ghostly fire dances are impossible to predict. However, scientists in Canada have spent over a hundred years studying the phenomenon and have teased out some trends. Some years are better than others. It turns out that solar activity (solar flares, mass ejections and other radiation) goes through a relatively predictable 11 year cycle that should be hitting its peak sometime over the next few months.  Besides being a treat for aurora watchers, this intensified light show will be invaluable for researchers looking for ways to protect our satellite and communications networks from this increased radiation. While they may be beautiful, the ions spiralling through space can, and have, wreaked havoc on our electrical grids.

This year’s maximum has turned out to be the weakest in over a century, but there are still lights to be seen.  So, look up, look waaay up and hopefully you will have the chance to experience a true natural wonder.

P.S. to find out when and where your best chances for aurora spotting are, visit: www.gi.alaska.edu/AuroraForecast

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In the Bleak Midwinter

Insulation - chickadee warming its feetIt was minus 40 Celsius with the wind chill the other morning. The bite of the air stung any carelessly exposed skin and the snow squeaked like Styrofoam underfoot. Wrapped up in my shearling coat, I couldn’t help but watch in fascination as a nearby mountain ash came alive with foraging Pine Grosbeaks and the cheerful chirps of chickadees and nuthatches filled the frosty air, reminding me just how incredible these tiny winter residents really are.

Chickadees, for example, weigh not much more than 10 g, about the same as two nickles. Yet, they can survive quite comfortably in temperatures that would leave us frostbitten and shivering.

Winter birds accomplish this seemingly unfathomable feat in a number of different ways. Firstly, they’re wearing a down coat. Those of you who own one know just how warm they can be and for birds, that insulation is part of the standard package. Feathers are a remarkable insulator. Comprising only about 5 – 7 % of a bird’s body weight (that’s half a gram on a chickadee), the air trapped within them makes up 95% of that weight’s volume, creating a thick layer of dead air that traps heat generated by the body, preventing much of its loss even on the coldest of days. Many winter residents grow a thicker winter coat, much like mammals, augmenting their feather count by up to 50 %. Fluffing feathers increases their insulation factor even further (about 30%), making them a very efficient way to keep warm in the winter, so efficient, in fact, some birds, like Great Gray Owl can actually overheat in the summer.

While some species, like Ruffed Grouse and many owls, grow feathers, along their legs and feet, like fluffy winter boots,  most songbirds’ legs are bare, thin sticks of sinew, blood and bone exposed to the elements. Although birds can tuck these delicate structures up into the warm cover of down when temperatures really plummet, most of the time they’re out in the open. So, why don’t they freeze and why isn’t all of a bird’s body heat lost through these naked limbs? Bird legs are marvels of biological efficiency, having been streamlined by millennia of evolution into sleek structures with very little muscle and few nerves, using instead pulley systems of tendons and bone to accomplish movement. These tissues, along with their scaly coverings have very little moisture and are less likely to freeze than flesh and skin.

Birds also have cold feet. Using a common natural system called a countercurrent heat exchange, our feathered friends keep their feet upwards of ten to twenty degrees colder than their core body temperature. Countercurrent Heat Exchange System in a bird's leg. by Heather HinamWarm arterial blood on its way to the feet pass right next to colder blood coming back towards the body through the veins. Heat wants to reach a point of equilibrium, so warmth from the arteries passes into the veins which carries it back into the body. Because the flows are running opposite to each other, it’s impossible for the heat balance to ever reach equilibrium, so by the time the blood gets to the feet, it’s much cooler than when it entered the leg and all that precious body heat has been kept where it needs to be, in the core.

However, as most of us who have experienced a true northern winter know, a coat alone isn’t always enough. There has to be heat to trap in order for insulation to work over the long term. To generate that heat, many winter birds shiver constantly when they’re not moving. Ravens, whose feather count isn’t as high as some of its more fluffy distant cousins, actually shiver constantly, even when flying, the repeated contractions of their massive pectoral muscles acting like a furnace. Powering that furnace takes energy and cold-weather specialists meet those needs by upping their metabolic rate, in some species, to several times their normal levels. As a result, food is always a going concern in winter.

Many winter residents can only forage for food during the day, so keeping the internal fires burning at night can be a challenge.  Finding a warm place to settle in for the night reduces those metabolic needs.  Densely-packed spruce boughs or old tree cavities are perfect nighttime microclimates and many birds use them. Chickadees will often take it a step further, piling as many fluffy little birds as possible into an old woodpecker hole to share body heat, which may just be too much cuteness in one place. Ruffed Grouse take advantage of the insulative capacity of snow in a somewhat comical way. One cold nights, the birds dive head first into a drift and tunnel deeper into the snow, creating a cave known as a kieppi. Temperatures inside the kieppi can hover just around the freezing mark, even when it’s minus thirty outside.

So as we close in on the shortest day of the year and sink deeper into the cold clutches of winter, take a moment, now and then, to marvel at those tiny survivalists outside your window. Much of the technology that keeps us from succumbing to winter’s icy grip was adapted from them. Nature truly is our greatest teacher.

Moonlight Becomes You

Luna Moth by Heather HinamSome childhood memories just seem to stick with you, lodging in your grey matter and coming back to haunt you at random intervals.

One that has been showing up quite frequently on the mental playlist lately harkens all the way back to a stint at Girl Guide Camp at Bird’s Hill Park, just northeast of Winnipeg over 20 years ago. It was a dark and muggy mid-June night as we trucked off as a group of giggling girls to the public washrooms. In the orange haze of the sodium lights, we heard a shriek of fright and immediately thought a bear had found its way into the campsite. Nervous, we crept around the corner toward the source of the sound and found girls from another troupe cowering under the lights over the door, pointing to the wall.

The source of their terror? Luna moths.

Looking back, I can see how these fluttering, green giants could scare the bejeepers out of a bunch of city girls. However, I was more fascinated than frightened by these enormous moths; still am.

I went a couple decades without seeing them again until one June day a few years ago. A friend came into work at the resort on Hecla Island and announced that they had a giant green moth on their door screen. Needless to say, I was over there with the camera in short order. The image above was the result.

There’s just something compelling about these ghostly green insects that float, like the moonbeams their named for, through the early summer nights.  With a wingspan of about 4 inches, they’re one of the largest moths in Canada and arguably one of the most beautiful; but few people get the chance to see them. They’re nocturnal and only exist in their adult form for about a week, so to catch a glimpse of these beauties, timing is truly everything.

They actually have a lot in common with a much more abundant and much less revered insect that emerges a few weeks later here in the north woods, namely the fishfly. Like its very distant cousin, adult luna moths have one purpose: to mate and deposit eggs to ensure the next generation. Like fishflies, these Saturnid moths have no mouths and do not feed. Their large, fuzzy bodies and consequently larger energy reserves from their larval stage allow them to live longer than the fragile fishfly.

In the dark labyrinth of the nighttime forest, finding a suitable mate is hard work, so male lunas can travel kilometres, tasting the air with their antennae for the pheromones drifting from a ‘wick’ extending from the abdomen of a waiting female.  Because they’re needed for this function, the antennae of male luna moths are much larger and fluffier than those of females, making the sexes fairly easy to tell apart. The moth pictured above is a female. Once the sexes find each other, they lock together in copulation for up to 20 hours before she sets off to lay her eggs. A female can produce up to 300 eggs, scattering them around the forest, a half dozen or so at a time, on the underside of birch leaves to incubate for almost two weeks.

The larvae are just as impressive as the adults, a bright, almost fluorescent green caterpillar that you can find trundling along the trunks and branches of its host plant, munching away on the leaves and growing up to 4 inches long by the time it sheds its exoskeleton for the fifth time (a process known as ecdysis).

Up here in Manitoba, where the summers are not long enough to allow for two generations, lunas overwinter as pupae in their cocoons. It isn’t until the following June that they will emerge from this stasis, all crumpled and fragile. Slowly, over at least half an hour, the new moth will pump hemolymph (insect blood) into their wings, ‘blowing them up’ until they harden into their characteristic green sails. It’s an event you can witness first-hand if you’re lucky enough to find a caterpillar before it pupates and keep it at home over winter. I’m actually planning to try and do just that later this summer so that I won’t miss the emergence of one of my favourite denizens of the dark.

The Edge of Darkness

Owl SilhouetteAs I’ve mentioned before, I have always had a love for obscure words, especially those that find everyday use in the lexicon of certain specialties.

Crespuscular is one of those words.

I use it all the time, but it’s definitely not common knowledge, something that’s become increasingly obvious over the many years that I’ve been a nature interpreter. I’ll throw it out there, along with other natural history terms, like ‘nocturnal’ or ‘carnivore’. While my charges usually nod sagely in understanding at these other adjectives, ‘crespuscular’ usually elicits furrowed brows and working tongues as they try to wrap their mouths around the syllables, eyes rolled up towards their brains, as though watching it try to divine the word’s meaning.

It’s too bad, because it’s a good word. It’s also a great way to be. A crepuscular animal is one that is most active at twilight, straddling the line between night and day in the muted light of either dawn or dusk. It certainly my favourite time to be out and about, probably because I’m in such good company.

Many animals are crepuscular in their habits; the most notable of which,  for me, are the owls. Species, like the Great Gray Owl, are at their best at this hazy time of day, making use of their enormous eyes and highly-tuned hearing to pick up the slightest rustle of prey along the forest floor. Owls, however, are not the only birds that enjoy this shoulder time. Common Nighthawks and Wilson Snipe also come alive in the dusk, the former swooping and diving through the gloom, scooping up millions of flying insects that have taken to the air after the heat of the day before the cool night temperatures slows their metabolisms and forces them back to earth. Most songbirds reserve their choruses for the crepuscular hours; Olive-sided Flycatchers announcing the dawn and Hermit Thrushes heralding the dusk, their refrains rounded out by the harmonies of breeding frogs.

Most boreal mammals are also crepuscular in their habits. The dull grey winter coat of the white-tailed deer is at its most invisible in the murky hours of twilight, especially to the mostly colour-blind vision of their carnivorous predators. Bats join the nighthawks in their aerial quest for a meal and rabbits emerge from the shadows, taking advantage of the low light to grab a quick nibble before complete darkness makes it difficult to spot approaching danger.

In reality, the busiest time of day, in whatever habitat you might live, is twilight. So, whether you are an early bird, who rises before the dawn, or a night owl, like me, who takes comfort in the release of the day as the sun slips below the horizon, get outside at these tenuous moments and discover the beauty and wonder of becoming crepuscular in your habits.

Can you hear me now?

Close up of a Great Gray OwlSomehow I’ve managed to make a good part of my living for the last decade standing around in the dark. Owls have been a source of fascination and a subject of study for me for quite a while now.  I’m not alone in that fascination. Many people are drawn to their seemingly all-knowing eyes and wise faces.

I hate to destroy any long-held beliefs, but owls aren’t really all that wise. There are many bird species (the crow family, for example) that have much greater levels of intellect.

That doesn’t mean owls are any less remarkable. This group of birds has evolved some amazing adaptations to help them make the most of their nocturnal realm.

What I find most fascinating is their ability to hear in three-dimensions. While we can perceive depth with our eyes, they can also do it with their ears.

Owl Skull (without sclerotic ring) showing ear openings.

The secret is asymmetrical ear openings. In most animals (ourselves included), the ears tend to be at approximately the same level on either side of the head. However, in the especially nocturnal owl species or ones that predominantly use hearing to locate their prey, one ear is usually higher than the other.

As a result, sounds do not reach both ears at the same time. It’s this delay that allows the bird to figure out where the sound is coming from.  They can be quite precise, detecting differences in timing up to 30 millionths of a second. When an owl hears a sound, the medulla of the brain creates a three-dimensional mental map of where it’s located. They then hone in on that point by moving their heads until both ears are hearing the sound at the same time. When they reach that point, they are facing their prey. Adjustments can be made while in flight, moving their heads until they’re lined up to strike.

Because they are operating at such a high level of precision, it’s important to have the best hearing as possible. In many owls, like this Great Gray Owl above, most of their face is made up of a disk of feathers. This facial disk acts like a satellite dish, funneling sound to the ears. Muscles under the skin allow them to adjust the shape of the disk as needed to get the best reception. Cup your hands around your ears and you’ll get an idea of how it works.

The size of this disk of feathers is a pretty good way to quickly assess just how nocturnal an owl species is. Larger disks, relative to the overall size of the face (like in Boreal Owls or Barred Owls), means that the species tends to hunt mostly at night.

Great Grays are a bit of an exception.  They have huge facial disks, but hunt mainly at dawn and dusk. These owls, however, hunt prey that are hidden by layers of snow in the winter. Like hunting in the dark, they can use their ears to pinpoint a vole running under the snow up to 150 metres away! It gives a whole new meaning to good reception.

Jack Frost Nipping at Your Nose

Frost is pretty much a defining characteristic of this time of year. Winters in the north woods get pretty darned cold. Our daytime highs have been in the -15 to -20 degrees Celsius range lately and the nights have been dipping down as low as -30. It’s the type of weather that takes your breath away, crisp and clear and, once you bet used to it, really very beautiful.

Winter nights in Manitoba can be perfect for creating what is one of my favourite spectacles: hoar frost.  On clear, cold nights, much of the earth’s heat gets sucked up into the atmosphere’s abyss, leaving the surface cooler than the air around it.  When that happens, frost forms, growing in dendrites from every available substrate.

I can still remember my first experience with hoar frost. I was a child and waking up to the world fringed in sparkling white was like walking into a dream.

While it’s gorgeous on a grand scale, it’s equally amazing when you get up close and personal, each tiny crystal spreading out into the air like tiny ferns. Each fragile structure grows as the frigid air can no longer retain the water vapour within it, depositing thin blades of ice at the tip of each branch.

So, if you’re lucky enough to live in an area that freezes from time to time, take a moment and the fragile and ephemeral beauty that is frost.