Under Pressure

With the ‘polar vortex’ that held much of North America in its frigid grip last week, it was interesting for this ‘girl of the north’ listen to southerners goggle about phenomena that I’ve been experiencing for most of my life.

I found one event, in particular, rather interesting. Last week, the media and thus a large portion of the population, was introduced to the concept of ‘frost quakes’. Torontonians were rattled out of their beds by thunderous booms that shook parts of the city at random intervals. Soon the headlines were reading that it was so cold in Canada, the ground was cracking.

Large crevasse in the rock, likely split apart by frost action

Having spent a number of winters on the shores of Lake Winnipeg, where  temperatures regularly dip below -30C, I’ve seen first-hand the power of ice and its ability to snap rock in two. Ice expands and contracts with temperature fluctuations. It also becomes less flexible as it becomes colder. Water that finds its way into fissures in the rock or soil can push so hard went it freezes – especially if the temperature drops quickly – that the substrate buckles under the pressure. Here, along the lake, the limestone cliffs are full of cracks forced open by winter’s icy push. Still, these earth-shattering events are extremely rare. You don’t usually see new cracks on a yearly basis.

However, there is another type of frost quake, or ice quake, as I prefer to call them that happens considerably more often. Based on where the events were reported last week along Lake Ontario, I’m willing to bet that it was this type of cryoseism  that residents heard for the most part. While the ground doesn’t crack very often, the ice on the lake does. On large lakes, like Lake Winnipeg or Ontario, a sudden snap of the ice can sound like a cannon shot, nearly knocking you off your feet and rattling windows in their panes. While it’s still not something you experience everyday, such quakes happen on Lake Winnipeg fairly regularly.

That’s because this 23,750 sq km lake freezes completely to a depth of at least a metre every year. That much surface area can’t solidify into one piece. So it freezes into floes that knit together much like the tectonic plates of the earth did when the crust first formed. Like the earth’s crust, the lake’s surface is full of fault lines, or pressure ridges.  These giant cracks can run for kilometres along the lake and usually form in about the same place every year.  Some ridges, known as stamukhi, are grounded along the shoreline, where ice that is held fast to the shore meets the free-flowing ice of deeper waters, while others run along over top of varying depths.

Even frozen, the lake is very much alive and pressure ridges are the sites where this is most noticeable. It’s along these lines that the ice floes move, sliding along, away from and into each other. A particularly violent collision is like a mini mountain building event and along with an ice quake, you will also see a ridge of ice has been pushed sometimes more than 2 meters into the air.  More often, however, the two floes simply press against each other, expanding and contracting like long, drawn-out breaths as the temperatures wax and wane. Eventually, the pressure overtakes the compressive strength of the ice and the ridge snaps in a startling bang that is often followed by the gentle whale-like ‘whoom’ sounds of the pressure waves dissipating through the rest of the ice.

As fascinating as they are, pressure ridges are also dangerous places to be. The ice floes can slide away from each other just as quickly as they can come together and loose plates of ice can trick the unwary into thinking they are still on solid ground. A number of commercial ice fishermen have been lost through shifting ridges over the last century on the lake.

Unless you live along a lake that freezes regularly, Ice quakes are truly something few people get to experience. So, I’m glad that our recent continental cold snap gave more people the chance to learn a bit more about this fascinating phenomena and remember just how powerful nature can be.

Dust From a Distant Sun

Autumn 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

Flight of Dragons

Although growing up, I was very much a tomboy, climbing trees and mucking around in the bush and ditches near my house, my relationship with insects was more typical of most city girls. I didn’t like them.  I thought nothing of swatting a house fly and I’m sad to say that I’ve run, screaming, away from a pursuing horsefly or the longhorn beetles that show up around August at the cottage.

However, as I’ve aged, my impression of insects has evolved quite a bit.  As I’ve grown to appreciate the amazing beauty and complexity of our natural world, I find myself drawn more often to those things that used to frighten or disgust me to re-examine them with my new perspective on life. I’m pleased to report that I’ve developed a new appreciation for longhorn beetles.

However, the one group of insects has always fascinated me, even as a child, is the dragonflies. I have a vivid memory of canoeing with my father down the La Salle River, south of Winnipeg, when a dragonfly landed on my knee.  I was rapt as I carefully held my lower half as still as I could while paddling to ensure my visitor a smooth ride, wanting to keep it with me as long as possible.

I’m not the only one with this fascination. There’s just something about these bejewelled predators that captures the imagination. I see representations of dragonflies everywhere, on t-shirts, in wind chimes and other household decorations, on jewellery and even fridge magnets. I think most people simply find them attractive, with their iridescent colours and delicate wings. They’re also ‘benevolent bugs’ from the human standpoint, voraciously devouring our ‘undesirables’ like mosquitoes and black flies.

Even with all of this goodwill, I don’t think the average person really knows all that much about them.  Dragonflies, and damselflies belong to the order Odonata (toothed ones), which contains some of the most ancient and largest insects ever known. There are over 5,900 living species, with nearly 100 of them found in Manitoba.

They’ve been around a long time, with the earliest fossil Protodonata (pre-dragonflies) dating to around 325 million years ago.  They were also a lot larger then, with wingspans reaching nearly a metre. I’m not sure we would’ve been so fond of them if they were still that size. When these insects first took to the air, they were the monarchs of the skies, feeding on whatever flew into their path. Vertebrates were only just crawling out of the water and so dragonflies had little competition and few predators. The benefits of being big, however, only lasted until dinosaurs started coming into their own.

Although they’ve become much smaller over time, the overall structure of a dragonfly hasn’t really changed all that much in 250 million years. These bugs are built to hunt on the wing. Their compound eyes are enormous relative to the size of their body and over 80% of their brain function is devoted to analyzing the visual input from the up to 30,000 ommatidia (facets) that make up each eye.  Having eyes made up of independent facets results in an incredible ability to detect movement because they can see in just about all directions at once.

This hyped-up visual centre can also detect parts of the colour spectrum that we can’t. Human eyes have three types of opsins, light-sensitive proteins that detect red, green and blue light. Diurnal dragonflies have four or five types of opsins arranged very specifically throughout each compound eye, with blue and UV receptors pointed up and longer wavelength receptors pointed down, likely to maximize their efficiency.

With amazing visual acuity, the ability to focus on one prey item at the expense of all else, almost all of their limbs facing towards the head and prehensile labia (mouthparts), they can snatch their prey out of the air with about a 95% success rate.

The last part of this deadly equation is their stunning aerial ability. We’ve all seen them dive and weave, hover and back-up, all while reaching speeds of nearly 50 km/h.  Dragonfly flight is actually very complicated, probably the most complex process of all flying organisms.  With four wings that can move independently of each other and dynamic airfoils that can flex around several angles, things can get complicated and scientists are still trying to sort it all out with the help of high-speed film.

They can make use of the classical lift that keeps planes in the air and a back and forth figure-eight stroke much like hummingbirds as well as take advantage of the vortices they create.  Some can turn 360 degrees around the axis of their bodies with the wings on one side stroking forward and the other side stroking back in one coordinated movement.  All of it is driven by a circuit of 16 neurons hard-wiring the brain to the highly developed motor muscles in the thorax.

So, the next time you catch the flash of a dragonfly as it zips along, take a moment to marvel at these truly ancient wonders of the natural world.

A Thing With Feathers

Even if you can somehow go through your entire life without ever seeing a bird, chances are very good that you will still have some experience with feathers. Whether displayed in a  hatband, stuffed into a pillow or quilt or tied together at the end of a duster, feathers are a fairly ubiquitous part of the world around us and certainly the defining characteristic of the group of flying vertebrates we know today as birds.

But, have you ever given much thought to where they came from?

As it turns out, feathers have been around a lot longer than most people realize. As paleontologists find more fossils every year to slot into the puzzle that is the evolution of life on this planet, the picture becomes clearer and stories start to make sense.

When it comes to the story of the evolution of feathers, the first thing you have to remember is that birds are modern dinosaurs, having evolved from the lineage known as Theropods, whose ranks include those Jurassic Park villains Velociraptor and Tyrannosaurus rex.  However, what didn’t make it into the movies was the fact that, at the very least, Velociraptor was not only ferocious, but fluffy. At first, this detail was inferred from the discovery that many of its ancestors were feathered and some, like the bizarre, bi-plane like creature Microraptor gui, could fly. Then, a discovery of quill nobs, a trait seen in modern birds, on the forearm bones of one specimen confirmed it. Now an accurate representation of Velociraptor is something like a sleek, predatory ostrich.

Even more recent discoveries have put the assumption of a scaly hide in Tyrannosaurus rex into doubt. While they haven’t found specimens of this iconic dinosaur with feathers yet, a cousin from about 125 million years old China, named Yutyrannus most definitely was feathered. About the size of a bus, these are the largest feathered dinosaurs known to date.

So how far back do feathers go? In time, we can trace their existence at least 160 million years to chicken-like dinosaurs called Anchiornis, but these critters already had the highly complex barbed feathers we see in modern birds today.  Most evolutionary biologists agree that feathers likely started out as single, hollow,  hair-like filaments that became branched and barbed as needed over time. These have been found in many species, most notably, Sciurumimus, a dinosaur found very near the base of the Theropod branch. Described for the first time just last year, this species shows a spectacularly preserved coat of dense, filamentous plumes. Finding feathers like these near the base of the branch suggests that maybe more advanced Theropods, including T-rex had some kind of plumage. Still, we don’t know just how far back down the tree they go.

The point of origin keeps getting pushed closer and closer to the root of at least the dinosaur’s evolutionary tree thanks to feather filaments being found in some Ornisthischian dinosaurs, like the Triceratops cousin, Psittacosaurus, who are about as far removed from Theropods and modern birds as a dinosaur can be. Actually, they’re starting to find feathers all over the dinosaur family tree, leaving us to wonder if they predate the group altogether. In fact, the genes responsible for taking an undifferentiated plate of keratin and turning it into a feather has been found in crocodilians, who although they are birds’ closest living relatives, branched off from the group well over 250 million years ago.

So what did these prehistoric feathers look like? Structurally, early feathers started out as simple, hollow strands, growing out from a plate of keratin embedded in the skin. More advanced feathers split into barbs, looking like fluffy ostrich plumes. Eventually, those barbs developed tiny barbules that allowed their wearers to ‘zip them up’, turning them into strong, but flexible sheets that eventually were co-opted into airfoils. This same evolutionary progression can be seen today in the growth of every bird embryo.

Most fascinating, however is the fact that paleontologists now know what colour some of these plumes were. Recent work with Anchiornis turned up microscopic pockets of pigment called melanozomes. By comparing these ancient structures to those known today, they managed to work out that not only was Anchiornis about the size of a chicken, it actually kind of looked like one, a bright tableau of shiny black and white spangles with a flash of red on a crest. Who knows, maybe in time, we’ll see our very own field guide to dinosaur plumage. Either way, you can’t help but marvel at these remarkable, ancient, ingenious  and unarguably beautiful innovations of evolution.

Moonlight Becomes You

Some 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.

I Want to Talk With the Animals

I’ve always had a bit of a Dr. Doolittle complex; but then, I think most of us have at some point, at least those of us who read nature blogs. Maybe it’s a by-product of having grown up with Disney movies full of talking animals and birds that sing along with your happy tune. Whatever the cause, I’ve always been looking for ways to make a connection with wildlife.

I feel very fortunate to have succeeded on a number of levels. Years as a field biologist have led to encounters of all sorts, from young owls hanging out in my pocket  and pulling moose out of sink-holes to being warned off by a pack of coyotes or nearly run over by an escaping fawn.

Lately, it’s been all about the birds. My local black-capped chickadees and red-breasted nuthatches have me trained. A few years ago, they descended on me one autumn afternoon, demanding food like kids on Halloween. One thing led to another and it quickly became a yearly tradition. When the days begin to grow shorter and the supply of insects dries up, my little masked bandits show up at the kitchen window, fluttering in front of the glass, letting me know it’s time to get out the sunflower seeds.

It’s an experience that will never get old: sitting on my back porch, hand out, while a half dozen or so chickadees flit between my outstretched fingers and the nearest trees, shuttling a seed or two back to their favourite hiding place. What fascinates me is how they come to trust in the first place.

It’s not uncommon for an animal to overcome its fear of humans for a good food source; but to come back year after year and to even seek me out in the first place is pretty remarkable when you think about it. However, for these species, a good memory can be the key to a long life. Resident boreal songbirds go through boom and bust cycles when it comes to food and will store the overabundance during the good times to help them through the leaner months. The trick is remembering where they put it.

Birds, as a rule, don’t have much of a sense of smell, so they can’t seek out food caches by picking up their scent, like a dog or a squirrel. They have to remember their hiding places. Chickadees are pretty good at it, finding a little over half of their nooks and pilfering any others they find by accident. Corvids, like ravens, crows and jays have even sharper memories, with some species being able to remember up to 80% of their cache locations. Like most of us, they use landmarks. Studies with Clark’s Nutcrackers have found that the birds take note of the relative position of rocks and branches to mark their troves.

Good memories in corvids also extend to who to trust and who is dangerous. Long-term studies at the University of Washington have shown that crows can remember people who’ve done them wrong for many years, harassing them whenever they get too close. So, if crows can do it, why not chickadees? But, how does this knowledge survive over several years? While crows can live for decades, the average lifespan of a chickadee isn’t more than two years.

Well, you know what they say, word travels fast. Chickadees are social birds with complex methods of communication biologists are only now getting a handle on. Those same studies in Washington found that crows pass on their knowledge to others within their range. Chickadees likely do the same. In fact, they manage to pass on their knowledge to others beyond their species. Turns out, nuthatches can apparently understand ‘chickadee’, at least when it comes to information about predators. I wouldn’t be surprised if they’re also picking up information about food by hanging around their ever-chattering flocks.

Once the snow melts, these flocks will disperse, scattering into the shadows of the forest to start their families for the year. In the meantime, their cheerful noise will bring warmth to the coldest of our winter days even if I can’t help but wish I could get in on the conversation.

Flying Away on a Wing and Prayer

For weeks now, the air has been full of motion, full of flapping wings and rhythmic calls.  Fall has been rolling over us like an endless wave, washing down from the north along ancient streams with millions of birds at its crest.

We’re deep into migration season here in the north woods. Actually, I’m sad to say that we’re getting close to the end. When it starts in mid-August, it’s a subtle change, a gentle trickle, as species begin to disappear like lights blinking out on a Christmas tree. It begins with the little guys, warblers, shorebirds and hummingbirds that have to make the long trek to Central and South America. One of the first of the larger species to go are the Sandhill Cranes (Grus canadensis), their warbling calls ringing so high up in the sky that you often can’t see them against the clouds.

By mid-September, most of the songbirds are gone and we’re knee-deep in waterfowl, thousands of Canada Geese (Branta canadensis), Snow Geese (Chen caerulescens) and assorted ducks darken the skies and fill the farmers’ fields on their way to the southern United States. Now, in late October, the last of the waterfowl are heading off and Bald Eagles are following in their wake, on their way to places where the water bodies don’t free solid.

In Manitoba, about 85% of our birds migrate, but how do they know when it’s time to leave?

Just like the leaves on a tree and pretty much every other living organism on earth, birds are tuned into rhythms of time, the waxing and waning of day length. As the days get shorter, it triggers a response in their hypothalamus that cascades from the brain through the endocrine system, changing the cocktail of hormones coursing through their veins, resulting in an itch to move that just won’t go away. Biologists call that itch ‘migratory restlessness’ or zughenruhe.

During this period, birds get antsy, staying up well past their normal bedtimes and eating like it’s going out of style. There’s a point to this sudden change in behaviour. Most birds migrate at night and it’s important that they store as much energy as possible for their long flights. In fact, migrants will increase their fat loads to anywhere between 15 and 50% of their body weight, depending on the length of their trip.

Many have a very long way to go, some travelling thousands of kilometres to their wintering grounds. Getting there takes a good sense of direction and birds make use of a lot of different tools. Like the explorers of old, the sun and the stars play a big role in keeping birds on migratory routes that have been passed down for thousands of generation. Because many birds migrate at night, the setting sun offers a quick and easy compass to use for orienting their take-offs. Scientists have confirmed this by studying captive birds and using bring lights as a substitute celestial body. Whenever they moved the light, birds would change their take-off orientation accordingly, ensuring they were headed in the proper direction.

It’s not always possible to see the sun or the stars and once you’re in the air, they become less useful. In many cases, large landmarks, like rivers and mountain ranges serve as highways, guiding the flocks on their journey. However, when all visual cues fail, they still have one more fallback. Deposits of the mineral magnetite in their brains have been found to operate as a built-in compass, allowing individuals to pick up the earth’s magnetic field and orient themselves appropriately.

Studies are still trying to sort out how this all works from a biological level, but there’s no question of its usefulness. Work with homing pigeons have shown that messing up the electrical fields around the birds’ heads made it impossible for them to navigate accurately by scrambling their magnetic reception.

So as you watch a V of geese winging their way overhead, just take a moment to watch them. What you’re seeing is an amazing confluence of adaptations and millenia of evolution that have resulted in one of the most astonishing natural phenomena on earth that can be witnessed just about anywhere by anyone.

And I see your True Colours Shining Through

My favourite season tends to depend on my mood, but most often, my answer is autumn. It’s refreshing, a cool breeze washing away the heavy haze of summer. Paradoxically, it also feels warm, like shrugging into your favourite coat as you catch a whiff of someone’s wood stove in the crisp morning air.

I think it’s the colours of fall that give the days their warmth. The cool greens slowly fade into yellows, golds, russets and umbers. The forests are suddenly ablaze with a riot of hues.

In the boreal mixedwood forest where I live, the dominant colour is yellow. The poplars and birches sparkle with it against the sapphire September sky. Still, if you look closer to the ground, you can find a little more variety. The dogwoods (Corylus stolonifera) go purple, their leaves a lovely compliment to their reddish branches. The mountain maple (Acer spicatum), like the one pictured above, show quite a bit of variation, ranging from a pale yellow in individuals that are growing in the shade to brilliant orange and deep red for those lucky shrubs that are exposed to full sun.

But, where do these colours come from?

To a certain degree, they’re always there, hiding just below the surface, waiting for their curtain call. New, functioning leaves are full of chlorophyll, a brilliant green pigment that is packed into structures within the cell appropriately known as chloroplasts.  These are the food factories for the tree, working throughout the growing season to transform carbon dioxide and sunlight into nourishing sugars via photosynthesis that are then funnelled into the rest of the tree. During this period, chlorophyll is constantly being degraded and replaced, keeping the leaves a brilliant green, overshadowing any other colours lurking within.

However, as the days become shorter and the sun’s intensity begins to wane, these factories shut down, using up their last stores of chlorophyll until there’s nothing left. Once the green is gone, the veil is pulled back giving other the hues a chance to shine. Carotenoids, a pigment that also plays a role in photosynthesis, remains, painting the trees with bright yellows and oranges. Some leaves also contain pigments known as anthocyanins, a watery dye that stains leaves with intense washes of reds and purples.

Just how bright and varied the fall palette is depends a lot of the weather. Warm, sunny days, followed by cool, but not frosty nights gives the leaves a chance to build up a lot of sugars and trap them within their cells. High sugar levels often results in greater amounts of anthocyanin, yielding more reds and purples, adding to the variety in the forest.

This year’s fall in the north woods has been just the kind we need for a spectacular display and the trees have not disappointed. Every day for the last few weeks, I’ve watched in awe as more and more of the canopy sparkles with colour, filling in the autumn landscape, a spectacular display against the clear blue skies.

Still, all good things must come to an end. Eventually, the nights get too cold and the days too short, signalling to the tree that it’s time to lock down for winter. The veins bringing moisture to the leaves close up and the branches seal over, cutting off the leaf’s lifelife. The late October winds howling off the lake will tear the foliage from their bases, sending them fluttering to the forest floor and returning their nutrients back into the soil to feed next year’s crop. However, those days are a little ways away, and in the meantime I plan enjoy nature’s yearly blaze of glory for as long as I can.

Double Rainbow All the Way

There’s just something about rainbows. They’ve been immortalized in endless songs, myths, stories, movies and even cellphone commercials based on the painfully hilarious mushroom-induced exaltations of an overly-enthusiastic youtube star.

Rainbows just capture the imagination. For the vikings of old, they were the Bifrost Bridge between Asgard, the home of the gods and our world of Midgard. In ancient Rome, they were the path of a messenger between Earth and the heavens and of course we all know they’re where leprechauns store their pots of gold.

But what are they really? Why can you never find the rainbow’s end? I think Kermit the Frog had it right when he labelled them ‘only illusions’.

Rainbows are the product of an observer standing in the right place at just the right time. What is that right place? It’s about 42 degrees from the direction opposite the sun. You can never get to the end of the rainbow because it will keep moving with you as you walk towards it. Stray off the bearing and the image will vanish into the mist.

What you’re seeing is sunlight being refracted, dispersed and reflected back at you through millions of water droplets suspended in the air. You usually only get enough water hanging around after a storm has passed, hence the name ‘rainbow’. Of course, if you’re standing next to a waterfall, fountain or someone’s sprinkler, you can often get the same effect if you’re in that magical optical sweet spot.

I’ll try and keep the physics simple, but here’s how it works. The white sunlight enters the water droplet and is dispersed into the full spectrum of colours. Then, it’s reflected off the back of the raindrop, just like the inside of a camera. On the way back out of the drop, each wavelength is refracted (their direction of travel is changed) as it passes from the water back out into the air.  How much each wave is refracted depends on the wavelength (colour) of the light. Red light (short wavelengths) are refracted less than blue (long wavelengths). The result is what was once a beam of ‘white’ light is now spread out into an arc of continuous colour. Double rainbows appear when the light is reflected off the back of the droplet lens twice. This second fan of light comes out at a slightly different angle and the spectrum of colour is inverted.

To us, the viewer, we see that colour in bands of red, orange, yellow, green, blue, indigo and violet because of the way photopigments in our eyes receive the light that is then interpreted by our brains. Take a black and white photo of a rainbow and you won’t see any bands, just a continuous gradation in intensity.  Animals whose brains can interpret wavelengths we can’t, like ultraviolet or infrared, would see a completely different rainbow than we do.

I think that’s what I find so fascinating about rainbows. Their beauty is truly in the eye of the beholder.

I’m Learnin’ to Fly

I’m always on the lookout for wildlife, even when I’m driving 100 km/h down a highway. My sister used to always get annoyed at my penchant for pointing out hawks circling overhead or braking suddenly to check out some mergansers along the lakeshore.

Well, the other day, my wandering eyes paid off. I spotted frantic flapping atop a hydro pole and had to pull over. It was definitely worth the stop, as I found myself watching a couple of juvenile Ospreys testing out their wings under the watchful eyes of their parents.

Over and over again they flapped furiously, gaining loft, but holding onto the branches of the nest like a ballerina would a barre. It was truly an amazing moment to witness.

Birds aren’t born knowing how do fly, just like humans aren’t born knowing how to walk. First off, it takes time to develop the enormous pectoral muscles needed to create and sustain the thrust required to get them off the ground and keep them in the air. Although most species lighten the load with hollow long bones and lungs that extend into air sacs throughout much of the body, the muscles responsible for flapping their wings make up 25-35% of a bird’s mass. These take time to develop; how much varies from species to species.  In Osprey, it’s nearly two months.

During that time, they practice, flapping and fluttering awkwardly and sometimes falling altogether. In some species, parents encourage the process by landing farther and farther from the nest with each food delivery, forcing their offspring to come out of their safe haven.

That fragile period in a bird’s life known as fledging is a bit of a behavioural tug-of-war between the demands of the young and the desires of the parents. It’s really not all that unlike human parents trying to get their grown up children to move out. Young birds don’t really want to leave the nest. I mean, why would you? You’re relatively safe, cozy and mom and dad bring you food several times a day. Sure, it gets a little cramped being crammed in there with your siblings and your room isn’t always the cleanest, but you don’t have to go out and work for your food. What’s not to love about that?

The thing is, parent birds need a break by the time young are ready to fledge. They can lose a significant amount of their body mass as a result of the energetic demands of feeding and protecting their offspring. Some species still have time in a season to raise a second brood, potentially doubling their genetic payoff. So, they want to get the kids off and into the world as soon as possible. Scientists have been studying this clash of wills for a long time now, measuring the costs and benefits on both sides of this ‘parent-offspring’ conflict.

When that conflict is resolved depends a lot of the species. Small songbirds usually only spend a couple weeks in the nest and then another couple of weeks following mom and dad around, figuring out how to feed themselves, but still begging for a handout whenever they can. For raptors, the period is much longer; osprey can take up to 17 weeks to become independent. It takes time to learn the art of hunting your own prey.

Young raptors learn by watching and again, through practice. I’m sure that for each generation of raptor there are mice and fish out there who’ve had a few years shaved off their lives from the terror of a near miss by a rookie owl or osprey careening towards them.

Still, they eventually get it right. They have to; at some point, mom and dad decide that they’ve invested enough into this generation and cut the chord. Because, regardless of the species we all must stand on our own two feet.