Restless Heart

Zugunruhe - migratory restlessnessTo regular readers of this blog, my love of obscure words is not a new thing. Over the last few years, I’ve been creating these ‘definition images’ as my way of bringing life to some of the wonders of nature and the words used to describe them.

Looking back over them all, I realized, much to my surprise, that I’ve crafted more than 70 of them, covering just about every letter of the alphabet. That discovery has led me to challenge myself to visualize words starting with more uncommon letters, like  X, Qand Z. Kind of like an artistic variation on Scrabble.

Autumn has given me the perfect opportunity to address one of my favourite Z words.  It’s another one of those terms that comes up only in the discussion of natural history and animal behaviour and it never fails to raise a few eyebrows if you manage to slip it into regular conversation.

The word is Zugunruhe.

Zugunruhe is a combination of two German words = Zug, meaning to move or migrate and Unruhe, meaning restlessness and it together, the sum is really the combination of the parts: migratory restlessness. For a behavioural ecologist, it’s a word that tends to conjure up thoughts of autumn, or more specifically, late summer.

As the earth lumbers along its orbital path and those of us in the Northern Hemisphere find ourselves canting away from the sun’s warmth, many creatures get antsy. Birds especially are seized by a sudden disquiet and activity levels skyrocket. Sleep patterns change and if the individuals are kept in a cage, they start orienting their activity in the direction they should be migrating in. Most species go through a period of excessive feeding, needing to pack away as much energy as aerodynamics will allow for the journey that inevitably lay ahead. We see it all around us in the clouds of blackbirds roiling through the air or flocks of geese descending on a recently-harvested field. This period of restlessness is referred to as Zugunruhe by biologists who study animal behaviour and it’s a phenomenon observed both in the spring and in the fall, just prior to the mass migrations that move millions of birds along north-south flyways over the continent.

Here, in the boreal forest, it’s a phenomenon that usually starts in August. Our summers are relatively short and as soon as breeding is over, the preparation of the twice-yearly journey gets underway, especially in songbirds, who have to travel thousands of kilometres to Central and South America. With their time here so fleeting and the journey so long and fraught with danger, you can’t help but wonder, why go through all the trouble?

Why not stay in the tropics, where the weather is favourable and save all of the energy and risk associated with long-distance travel? The answer to that question likely varies to a certain degree between species; but evidence suggests that food, or rather the lack of it, was likely the driver behind the evolution of long-distance migration in many birds.

Most of today’s migratory species likely evolved near the equator, enjoying consistently tolerable weather and relatively abundant food. However, as populations started to grow and segment into different species, the pressure on food sources grew to a point where the survival of some depended on searching out new resources. The only place to go was away, into the temperate zones north and south of the tropics. Those that did, discovered abundant resources, millions of insects, and a glut of fruit and vegetation. The problem was it only lasts for a short period of time, forcing those explorers to retreat back to the warm haven to the south during the winter months.

Over millenia, these paths have been extended and entrenched by generations of birds winging their way along now well-established routes.  As those paths have become increasingly ensconced in the collective memories of each species, so has the irrepressible need to travel those routes that spurs everything from hummingbirds to harriers on their way twice a year.

With migration in full swing here in Manitoba, the period of zugunruhe is actually over; but once balance of night and day swings back into the favour of the light, the millions of birds enjoying the warmth of their winter homes will feel the inexorable pull once again, the restlessness building until one day, they’ll have no choice but to take to the air and find their way back to us.

Sweetness and Light

Portrait of Fireweed by Heather HinamThe first blush of spring flowers has long since faded, leaving forests and fields to settle into the rich greens and sunny yellows of mid-summer. Still, the decidedly verdant palette is broken now and then by a showy splash of pink, startling against the endless green, like flame in the darkness.

These tall, fuschia spires are fireweed, nature’s phoenix, rising out of the ashes of destruction and bringing colour back to the land. They also happen to be one of my favourite flowers; but not for a reason that’s immediately obvious. They’re actually rather tasty.

Nearly 15 years ago, I was fortunate to spend some time visiting a friend in the Yukon. We had an amazing time exploring the western edge of the territory, camping out in the shadow of the Rockies in the still long days of early fall.

In the airport on the way home, I spotted it, jars of a clear pink, gleaming in the fluorescent light of the gift shop: fireweed jelly. I had to try it and after tasting its delicate, sweet flavour, I had to figure out how to make it.

Turns out, the second part of that equation was harder than I expected it to be. Over 10 years ago, the internet was not as vast and I couldn’t find a recipe anywhere. After much searching, I ended up finding what I needed in a dusty old text squirrelled away in the Winnipeg public library.  I actually found a lot of ways to cook wild edibles in that book; but most coveted was my recipe that will work for any petal-based jelly.

We’ve been blessed with an abundance of fireweed this summer in Grindstone; but I’ve been so busy with other work that I haven’t had time to go out and harvest. It’s fairly time-consuming labour. Picking the flowers is easy enough. You just need a pair of scissors, long pants and something to store the feathery spikes in. Once you get them home, the fun part starts: separating the blossoms from the stem. I usually end up spending a good hour plucking the flowers, one by one, dropping them into a bowl and setting the green bits (which are also edible) aside. By the end, your fingers will be died purple and the rest of you will be crawling with crab spiders and leaf hoppers; but it will be worth it in the end, trust me.

Once you have your blossoms, stuff as many as you can into a pint sealer jar and cover the lot with boiling water.  Let the developing tea steep for 24 hours in a dark space (to keep the sunlight from washing out the delicate colour). Strain out the now leeched-white blossoms and pour the liquid into a deep pot, adding 1 1/2 cups of sugar for every cup of tea (3 cups to a pint). Add a teaspoon of lemon juice and bring to a rolling boil, letting it go for a good minute. Add 6 oz of liquid pectic to the mix and boil hard for another minute or so. Take it off the heat and skim any foam before carefully filling sealer jars and proceed to can it according to direction.

This recipe doesn’t make much, but it’s flavour is worth it. If you’re concerned about the colour once you’ve strained out the blossoms (sometimes it can look a little brownish), you can add a tablespoon or so of strawberry juice. It won’t affect the taste, but will keep it nice and pink.

Fireweed is one of those flowers that just seems designed to bring joy wherever it grows. As suggested by its name, its rhizomic habit makes them one of the first colonizers to bring colour back to a fire-blackened forest, springing up through the ash from runners in the underlying soil.

This year, the bright blossoms brought beauty back to the devastation wrought by Manitoba Hydro after they cleared the area around their power lines of shrubs and trees in my area. As my friend, Cindy mentions in her recent post on the same subject, thanks to their tenacious rhizomes that can knit their way through the soil up to almost half a metre deep, fireweed managed to find its way into the centre of London after the city was ruined in places by World War II bombs. To me this hardy denizen of northern forests and fields is a reminder to all of us that even in the face of humanity at its ugliest and most destructive, nature always manages to find a way to bring light back to the earth.

Given to Fly

Alight - Herring Gull LandingI never get tired of watching birds fly. It’s something that’s always entranced me: a warbler flitting between sun-dappled leaves, a gull wheeling lazily against the clear blue of a Manitoba summer sky, or the subtle whisper of an owl’s feathers as it returns to roost.

My fascination with flight started at an early age, much to the consternation of my parents who had to cart me off to the hospital to get my foot x-rayed after an ill-fated attempt to get airborne from the top of a ladder with willow branches strapped to my arms.

I’m pleased to report that there was no permanent damage and I now have a much better grasp on the mechanics of avian flight.

Physicists and biologists alike are still trying to sort out all of the details; but we get the general gist of how it works and much of that knowledge has resulted in the air travel we enjoy today.

A bird in the air has two forces to contend with: gravity (the inexorable force the earth exerts on everything, drawing us back to its core) and drag (the force of the air that pushes back against us whenever we try to move through it). In order to keep itself aloft, the wings of a bird must produce enough lift to counter gravity and reduce drag.

 

Much of that is achieved through the shape the wing. It takes a lot of energy to flap all the time to produce enough thrust to keep you up and moving forward, so having wings that can generate lift and reduce drag as you glide are a beneficial adaptation. Wings aren’t flat, whether they are on a bird or a plane. Diagram explaining how cambered wings create liftFlat wings don’t create lift. Air moving around a symmetrical wing passes over and under its surface at the same speed on both sides. However, if you curve the wing and create a cambered airfoil, then you’re getting somewhere. With a cambered wing, the air passing over the top moves much faster than the air passing below the wing. This creates a pressure differential, with lower pressure above the wing, where air is being swept away and high pressure below where air is piling up, pushing the wing and the bird attached to it, up into the sky. There wasn’t much camber to my willow branches, hence the crash landing.

 

Diagram explaning how the angle of attack of a wing can affect liftAnother way increase that pressure differential is to tilt the leading edge of the wing up, dropping the flight feathers down and building up more air underneath. However, you can go too far with this. Tilt more than about 15o and the airstream separates from the upper surface of the wing, creating turbulence, stalling the bird out. They use this to their advantage when landing, like the gull in the image above. To control the stall, most birds can raise their equivalent of a thumb called the alula. This nub of bone with usually about three feathers on it (you can just see it sticking up behind the top of the gull’s wing in the picture) can split the airstream at the leading edge, forcing it back over the surface of the wing.

 

 

 

Once they’ve vanquished gravity, there’s still the matter of drag threatening to push them back to the ground. Flapping, of course, will keep you moving; but there are several design considerations that birds have made over millenia of evolution.  Birds that do a lot of gliding (e.g. gulls) have long, tapered wings that concentrate any vortices that might form at the wing tips (turbulence caused by the feathers slicing through the air) into two small areas that are as far apart as possible, reducing what is called ‘pressure drag’. Soaring birds, like hawks and Sandhill Cranes, take a different approach, spreading out their primary feathers like fingers, splitting up the wingtip vortices and reducing their impact.

If you found wrapping your head around all that was a bit of a challenge (like I did the first time I had to teach it), understanding what’s going on when a bird is flapping will give you a veritable headache. Things get complicated as the wing starts to move and lift and thrust start happening simultaneously. In a nutshell, however, the lift is generated by the curve in the part of the wing closest to the body, while the tips of the primaries produce the thrust, creating momentum that propels the bird through the air with a grace that always amazes me.

Sometimes taking a phenomenon apart and learning how each component works destroys the magic of the whole thing; but I haven’t found that to be the case with the flight of birds. Understanding the forces that make it possible for them to shed the earth’s shackles only makes it all the more remarkable.

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.

It’s a Hard-Knock Life

Juvenile Northern Saw-whet OwlsThere isn’t much else in the world that’s cuter than a baby Northern Saw-whet Owl. I should know; I handled dozens of them over the course of my doctorate research. Between their huge, blue, soulful eyes and the round, fluffy, ewok-like body, they’re guaranteed to evoke an ‘aww’ out of even the hardest-boiled egg of a person.

Still, most people will never have the opportunity to see one, at least not in their juvenile plumage. They’re notoriously hard to find.  Northern Saw-whet Owls nest in old tree cavities, moving into empty woodpecker holes and other crevasses in rotted out trunks. To study them more closely, researchers put up nest boxes in the hopes of coaxing them into more accessible real estate. It’s a lot easier to climb a ten-foot ladder up to a nest box than to have to figure out a way to get 25 feet up into a poplar or worse, a hydro pole.

Even once they’re out of the nest, they’re difficult to spot. Being not much bigger than a coffee mug full-grown, these little owls rely on camouflage to stay safe in the forests and woodlots where they make their home.  Their first line of defence when threatened is to go stock still against a tree trunk or in a mess of branches. It’s a very effective manoeuvre.  Adult saw-whets have stripes of brown and white on their breast feathers and spots on their heads that break-up their profile, helping them melt into the shadows. I can’t tell you how many times I’ve tracked a radio-tagged bird to their daytime roost and still couldn’t spot the little guy among the leaves. The brilliant white V on the forehead of juvenile birds is to help parents find their mouths in the dark of a nest cavity. Still, in daylight, this natural beacon manages to blend into the dappled sunlight on the foliage.

Adult Male Northern Saw-whet Owl

Adult male Northern Saw-whet Owl blending into the background.

So, any time I get to spend with these little guys is a treat, one that I never take for granted. It’s always such a pleasure to get to observe their individual personalities up close.

Don’t let their size and adorable expressions fool you. These are tough little birds. They have to be. Life for a Northern Saw-whet Owl is hard from day one. Females lay their eggs two days apart, but start incubating before they’ve completed the clutch. As a result, you end up with a nest full of young where the oldest may have a ten day head start on life over the youngest. In years where the small mammal population is high, the provisioning males can make their nightly quota of about seven or more prey items a night, making it possible for all the young to make it out of the nest. However, in years where food is scarce, that age difference suddenly comes into sharp relief and it’s not uncommon to find only one or two of the oldest nestlings surviving out of a clutch of 4-6.

Even if they make it out of the nest, life doesn’t get much easier. After a month crammed into the nest hole with mom and all their siblings, you’d think these newly-fledged saw-whets would want to move on and take advantage of their new-found freedom as quickly as possible.  However, despite having fully-feathered wings by the time they leave the nest (unusual for owls), juveniles tend to hang around the homestead for another month or so. They spend their days tucked away in the shadows in nearby trees and their nights calling insistently for food deliveries from their already beleaguered father, their mother having taken off around the time the oldest hit 21 days for a much-needed break.  During this post-fleding period, young saw-whets practice flying and refine their hunting skills.

Eventually, it’s time for them to strike out on their own into the great unknown. It’s actually a great unknown for us researchers as well. Despite a number of long-term banding programs for the species all over North America, we still don’t have a very good handle on saw-whet owl movements outside of the breeding season.

So every year, my colleagues across the country and I will keep adding new nest boxes and checking the ones we have, spending as much time as we can peering into the lives of these adorable and enigmatic owls in the hopes that one day we might unravel a few more of their mysteries.

* If you would like to entice owls to your backyard, let me know, and I’ll send you the plans for building a nestbox.

A Breath of Life

Poplar bud in springSpring is in full-swing here now. In the southern reaches of Manitoba, some trees have leafed out almost fully and many of the ornamental fruit trees are in full bloom. At home around the lake, however, things are moving just a little slower. The first blush of green is only now enveloping the forest and I find it fascinating how only a few hundred kilometers can make such a difference in to the rate of renewal after winter’s chill.

As with many natural processes, day-length does play a role, but the story here is much longer and more complicated than that. In fact, the stage for each spring’s grand entrance is set the previous fall.

The shortening autumn day signals to the tree that it’s time to enter into a period of dormancy, sort of a forced vacation, where all systems shut down to preserve the tree’s tissues and protect it from freezing temperatures and water loss. Before it enters into this stasis, the tree uses the last of its growing resources to form the buds for the following year, encasing these primordial leaves in waxy scales that hold them in place until they get the go ahead to continue development.

After everything shuts down for the winter, the process shifts into a sort of time-release mechanism. Each species has it’s own mandatory vacation period, a set number of cold days it must endure before any warming will trigger the growth of new leaves. That period, however, is usually shorter than the average Canadian winter. So if we get a sudden early warming, like we did this year in March, it can trigger the start of new leaves, which can then be a death sentence if the forest is then hit with another cold snap. Alternatively, really warm autumns or warm winters can delay the onset of budding by pushing back the point at which the ‘mandatory cold period’ started. This reliance on temperature to maintain their cycle may make it very difficult for trees to adapt to the rapid changes in climate patterns we’re starting to witness.

Here in Manitoba’s boreal, however the wave of green is sweeping across the landscape as it always has this time of year. It happens so fast, that if you’re not paying attention, you can miss the in between stages and those are the best parts.

My absolute favourite time is when the Balsam Poplar’s (Populus balsamifera) buds (pictured above) begin to swell to bursting. They’re full of sticky, volatile oils that fill the air with a warm heady scent, that’s a pleasant mix of vanilla, cut fir boughs and Vicks Vaporub. I’ll never forget my first experience with a Balsam Poplar stand in full bud. It’s an amazing smell that washes through you, leaving you both calm and invigorated all at the same time.

Balsam poplar buds in oil

Soaking up the sun – Steeping balsam poplar buds in oil, the beginnings of Balm of Gilead

The healing effect may not just be limited to your sense of well-being. For centuries, Aboriginals and European immigrants alike have used poplar buds for medicinal purposes, typically warming them in some sort of fat to draw out the oils and then using the resulting salve on everything from wounds, eczema, and rashes to lining the inside of the nose to clear up airways. I learned how to tease the benefits from the bud from a woman living in the farmlands north of Swan River, Manitoba.

After steeping the buds in a good-quality oil in the sun for several days, strain off the liquid and thicken it with beeswax. The result is known as Balm of Gilead and makes a nice skin cream that smells wonderful.  Beyond it’s fragrance, the oils also contain salicin, a compound similar to aspirin that has been used as an analgesic by many cultures.

Whether it’s grounded in chemistry or not,  I still believe there is nothing better for your health and well-being than getting out an experiencing the first breath of life that is spring in the forest and surrounding yourself in its fragrant, verdant beginnings.

Bright-eyed and Bushy Tailed

Red squirrelAfter charging out of the gate early and then several false starts later, spring is finally settling in here in the boreal forest.  It’s been a strange year so far and I can’t help but wonder worriedly at the changes I’ve been seeing in the climate these last several years.  Between summer-like temperatures, then snow and frost, it’s been hard to get true sense of the seasons.

The animals, however, tell a different story. Seasonal behaviour in most species is hard-wired to a certain degree, often tied in less to temperature and more to changes in the length of daylight.  While, unseasonably warm or cold days can either speed up or slow down nature’s clock, the overall pattern remains relatively constant.

For me, one of the first harbingers of spring comes in the form of a frantic ball of red fur streaking through the forest.  Red squirrels (Tamiascurius hudsonicus) are active all year, racing from tree to tree, industriously gathering up anything remotely edible and either devouring it on the spot or stuffing it away in a midden, the heart of their territory, for leaner times.

This flurry of activity takes a definite upturn as the darkness of winter gives way into the softer, longer light of spring.  Here in the boreal, that can be as early as the beginning of March, when patches of snow-free ground begin to appear on the forest floor. Females are only reproductively receptive for a day, but she’s not shy in giving her potential suitors a head’s up, bounding through their territories, days before her estrous, reminding them of their impending opportunity.

Squirrels aren’t known for their social grace or a warm and welcoming demeanor. These feisty little rodents are fiercely territorial, expressing their displeasure at anyone and anything that crosses into their domain with an insistent rattle that ricochets off the surrounding trees like a miniature jackhammer. Mating season is the only time of year that edginess eases somewhat and males welcome the presence of female intruders into their little patch of forest, hoping for a chance to pass on their genes. However, if another male crosses over the boundary, all bets are off and the territory holder immediately lays into the interloper, the two of them bounding through the forest in a flurry of fur and furious chattering.

Females are equally antisocial and once the deed is done and she’s been inseminated, the donor is no longer welcome on her doorstep. Like many mammals, red squirrel females raise their young on their own, tucking themselves away into an old woodpecker hole to set-up a home for their young.

Gestation is only a little over a month, so it won’t be long before the squirrels in my neighbourhood find themselves with new mouths to feed. The young are born blind and pink, completely dependent on their mother’s milk and warmth, tucked up in the whorls of grass with which she’s lined their nest. Nests are established opportunistically, and squirrels will just as easily set up house in a nest box intended for birds as in a natural cavity. In my years working with saw-whet owls, I’ve stuck my hand into my fair share of squirrel’s nests and come out with a palm full of very warm, very naked little babies.

They grow quickly, however, putting  on almost 2g/day until they’re ready to venture out on their own just over four months later. By that time, the little guys are fully furred, smaller replicas of their parents, with an innate ability to scamper through the trees without a second thought. That’s not to say there isn’t a bit of a learning curve. One can only marvel at their resilience when watching a juvenile plunge 40 ft out of the tree to the ground, dust himself off and climb right back up like it was nothing more and a stubbed toe.

Resilience is key if you’re a red squirrel. Once they leave the nest, times are tough. By the end of the summer, they are no longer welcome on their mother’s territory and must take up residence someplace else. Competition is fierce and predators, like marten, goshawks and owls are just waiting to make a meal of them. Still, squirrels are scrappers and if they can get a foothold in that first year of life, they’ll likely be just fine. So, spring settles in with fits and starts after an unnervingly warm winter, I can’t help but take comfort in the ringing rattle outside my window, reminding me that even with all that is changing around me, the seasons still cycle and life finds a way to move ever forward.

Flying with Dinosaurs

Canada goose and dinosaurSince the beginning of January, I’ve had the pleasure of teaching a second-year Chordate Zoology course at the University of Winnipeg. Having taken it at a different school as an undergrad and having taught the labs several years ago, the material isn’t exactly new. However, it’s been a wonderful way to rediscover the fascinating story that is the evolution of vertebrates.

First and foremost, it’s reminded me that we see dinosaurs just about everyday, flitting through the trees, soaring high overhead and gliding across a glassy pond. They’re all around us, bringing colour and music to our world.

Because of my grounding in zoology, the concept that birds are dinosaurs is not new to me, nor is it difficult to understand. However, I imagine for many people it’s a bit of a challenge to make the mental leap from a chickadee flitting among the leaves to a giant Tyrannosaurus rex thundering along a Cretaceous plain.  Still, whether you can see the resemblance or not, the genetic relationship is undeniable. A spectacularly rare discovery in 2007 of intact collagen protein in the fossil leg bone of a T-Rex allowed researchers to compare the amino acid chains within with a database of species we already have sequences for. It turned out that of all the possibilities, from mammals to reptiles, the sequence was most closely related to the collagen sequence of a chicken. This discovery probably would’ve left good ol’ Colonel Sanders with nightmares!

Even without the molecular connection, you can still see the family resemblance. Birds are descended from a lineage of dinosaurs known as Theropods, swift, bipedal predators, like Velociraptor, Deinonychus (pictured above) and the aforementioned T. Rex. While the ones most people are familiar with, thanks to Jurassic Park, are the large, ferocious creatures, most of this lineage were rather small, adapted for running and pouncing on their prey. These adaptations for speed and agility can still be seen in the skeletons of the last remaining dinosaurs, the birds.

They walked on two legs, their limbs swinging back and forth on the fulcrum of a pelvis that looked like part of a bicycle. Over time, that pelvis shifted, the individual bones fusing and getting stonger to withstand the strain brought by high speeds while maintaining its light weight. In fact, weight reduction was the order of the day in the evolution of birds from their theropod ancestors. Bones, overall, got smaller, lighter, hollowing out into tubes that were, and still are, reinforced by thin struts called trabeculae. The pectoral girdle got both smaller and in some ways, more rigid. Where the scapulae were freed up to allow the arms to swing out like flapping wings, the clavicles fused, forming the furcula (wishbone) and the sternum developed a deep keel, giving more space for what eventually became flight muscles to attach.

Still, the most striking feature these dinosaurs had in common with the ones we see today was feathers. That’s right, Creighton missed that little detail. Many theropods, Velociraptor included, had feathers. They started out as long, thin fibers that offered the minimum of insulation, gradually developing into the differentiated flight, covert and down feathers we know now. They appeared at least 160 million years ago, long before Archaeopterix (the first official bird) and even non-avian theropods like Velociraptor and Deinonychus. Paleontologists have found them in numerous species, including a small chicken-like theropod (the whole protein thing is making sense now) named Anchiornis. They’ve even managed to determine the colour of the feathers by examining the shape of the melanosomes (tiny pockets of pigment) preserved in the fossilized remains.

As more and more of these characteristics are teased from the fossil record, I can’t help but hope that one day my field guide to birds includes a section on the species that paved the genetic way for the spectacular diversity we see today.

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.

Sounds of Silence

White-tailed deerWalking through the winter woods I can’t help but feel an overwhelming sense of closeness with the world around me. Snow is nature’s greatest silencer, muting the world as it bathes it in white and it’s this silence that breeds a feeling of intimacy with my forest brethren. Shrouded by heavy bows and intermittent shadows, I feel my senses stretch through the quiet, reaching out for any sign that I’m not alone in my wanderings.

As I make my silent progress, I find myself wondering how the other inhabitants of the forest perceive this winter world. Whenever I get into one of these moods, my mind usually strays to the white-tailed deer, a species I’m fortunate to meet often on my woodland rambles.

We’re about the same size, a doe and I, and their soft, forward-facing eyes and expressive faces make them easy to relate to.

Though I know she could easily outrun me (especially since I’m a rather slow runner, even for a human), we have a bit more in common than we might first realize. White-tailed deer and humans perceive the world in much the same way. Deer, for the most part, are just a lot better at it.  They have to be. When you live you life under the constant threat of predation, it’s in your best interest to develop a sophisticated arsenal of early-warning systems and deer have plenty.

In deer, the nose knows everything that’s going on around them. With over 290 million olfactory receptors, deer can detect the faintest whiff of danger, even more accurately than their canine pursuers (who only have about 220 million). Both, however, seriously outstrip humans, with our rather paltry 5 million. Where do they put them all? The nasal region of both cervid and canine skulls is actually quite long and full of thin bones in a delicate scroll-work called nasal turbinates. In the living creature, these bones are covered with olfactory epithelium (skin with scent receptors) that picks up the tiniest of molecules. When actively sniffing, they fill their nasal cavities with as much air as possible, giving scent molecules a better chance of being picked up.

To further improve things, deer have a small, fluid-filled sack lying just on top of the palette called the vomeronasal organ (or Jacobson’s organ). This seems to function in a very specific type of scent detection – pheromones, something most mammals use in abundance and deer are no exception.  Whether we have such a functioning organ too is still being debated, but there is evidence that suggests it might play a subtle role in our lives.

Whenever I come face-to-face with a deer, I’m always drawn in by those liquid doe-eyes and this is one place where we have a bit of an edge over our four-legged friend, at least when it comes to how we see our world. Most people will tell you that mammals, especially ones that are active in the dark, don’t see colour. That’s not entirely true. The retina of deer eyes do have cones (colour receptors); they just can’t quite distinguish the same spectrum. A deer’s world is tinted in blues and greens, which makes sense, considering their main concern is picking out the right plants to eat. Still, don’t think you’re invisible to them as you walk through the woods in a blaze-orange vest. Recent work has found that they can pick out at least a hint of these longer wavelengths and with a visual range of 300 degrees while standing still and eyes that are highly sensitive to the slightest movement, a deer will notice you long before you even know you’re not alone.

Besides, if the eyes fail them, the ears wont. No matter how carefully I tread, I know that somewhere, the crunch of my footsteps is being collected by the large, rotating pinna of a deer’s ear. Their range of hearing is considerably better than ours, picking out much higher frequencies than we could ever hope to detect. The wide placement of the ears on the head and their ability to rotate them independently also make it possible for a deer to triangulate the source of a sound, much like an owl.

I know that I will never experience the world on the same level as any of my fellow forest inhabitants, but on a silent, snowy afternoon, I can’t help but want to try.