Flight of the Bumblebee

Bumblebee pollinating fireweed by Heather HinamIt’s been a long, long, long winter here in the north woods. Then, suddenly, it was summer. The browns and greys of last year’s decay vanished nearly overnight, replaced by the verdant greens of new growth. Flowers are coming up everywhere and the air is alive with insects. That last part doesn’t get most people up here all that excited. A large proportion of those insects at the moment are mosquitoes. However, trundling along through the clouds of bloodsuckers are the pollinators.

One of my favourite groups of the myriad species that call this region home are the bumblebees (Bombus sp.), the flying teddy bears of the insect world.  While most members of the Order Hymenoptera, like wasps and hornets, tend to send people running in the other direction, bumblebees hold a special place in the hearts of even the most nature deprived. Their brightly-coloured, fat, fuzzy bodies, topped with almost comically small wings, coupled with their almost roly-poly nature makes even the most hardened insect-hater melt a little bit on the inside.

Unlike honeybees, bumblebees are native to North American. There are a few dozen species that have fit into just about every niche across the continent, making up what may be the most important assemblage of pollinators we have.  What makes them so efficient at the job is their hairy bodies. Bumblebees feed on nectar and that is usually stored near the centre of the flower. As the bumblebee noses its way deeper into the blossom, the pollen-laden stamens brush against the insect’s body, transferring its important cargo to be transported to the next blossom.

While they do collect that nectar, bumblebees are not honey producers. Unlike the species we’re mostly familiar with, bumblebees are only semi-colonial, setting up small nests that only last for one year. It all starts once the frost is out of the ground. Queen bumblebees overwinter by themselves in the leaf litter or underground. Once she wakes up, her first order of business is finding food. With the late winter we had this year, she likely would’ve had a harder time than usual.

Once she’s managed to restore her energy levels, the queen will set up shop in a quiet, dry place like a woodpile, old rodent hole, tree cavity or even a nestbox. There, she will lay her first clutch of eggs, which she’s incubates in the most adorable fashion by sitting on top of them and ‘shivering’. To feed herself and her young larvae once they hatch, the queen gathers nectar that she stores in her nest in little wax pots.

That first generation of bees are all worker females, who quickly take over the foraging duties, bringing home more nectar and fashioning more wax pots, upon which the queen lays her subsequent eggs. Workers also take on guard and cleaning duties while the queen remains in the nest, taking a well-deserved rest and generally ruling the roost.

As the long days of summer begin to wane, the queen plans her insurance policy for the following year, laying eggs that hatch out both males and new queens. Both of these cohorts leave the nest and somehow find each other in the big, bright world outside of the colony.

Once mated, those new queens head off to find a place to hunker down for the winter while the home there were born from fades away.  It’s a system that’s worked for thousands of years, ensuring the proper functioning of pretty much every ecosystem in North America. Unfortunately, now, it’s in trouble. Like most pollinators, bumblebees are facing hits from all directions. Losing both nest and food sources to habitat loss from large-scale agriculture, timber harvest and urbanization, they are also having to contend with pesticide usage turning the plants they depend on into death traps.

However, if we, as a populace, make a conscious effort to change the way we do things, curtailing bee decline is not an insurmountable problem and every individual counts. By planting bee-friendly species in your yard that come from growers you know don’t use pesticides, you’re creating a haven for these beleaguered bugs. Talk to your greenhouse owners, talk to your representatives. There’s more and more data showing that certain types of chemicals are the problem and need to be taken off the shelves and out of our food production. We’ve done it before with DDT. We can do it again.If we don’t, the world as we know it will cease to function. It’s as simple as that.

For those of you who are a little less insect-inclined, it’s also good to remember that bumblebees are nothing to be afraid of. While they can sting, they’re pretty mellow individuals and if you take precautions like not wearing strong perfumes and running around barefoot, you’ll have no trouble co-existing peacefully with these fuzzy, buzzing, beautiful and essential bugs.

 

 

 

Jumpin Jack Flash

White-tailed Deer Flagging by Heather Hinam

If you’ve ever spent any time in North American forests east of The Rockies, you’ve seen it, a sudden flash of white, that snags your attention before disappearing into a tangle of vegetation.

White-tailed deer  (Odocoileus virginianus) are very aptly named.  The bright, snowy fur on the underside of their tail is impossible to miss, especially because they often wave it in the air as they bound away from you.

This behaviour is called ‘flagging’ and it’s an instinct that kicks in only hours after birth.  To a human observer, its purpose is a little hard to understand. Why would an animal that is otherwise very well camouflaged wave a big flag at a predator that essentially shouts “I’m over here!”.  Because it seems so counter-intuitive, flagging has been the focus of a number of studies, but researchers still have yet to come to a consensus in regards to why they do it and who are they doing it for: their fellow deer or whatever is trying to make them dinner.

Some biologists believe that by flagging, their tails at the approach of a predator, deer are signalling each other and maintaining the cohesion of the group while at the same time confusing their stalker by making it hard to pick out an individual in the group.

The problem with that assessment, however, is that deer will flag when they’re by themselves or when others in their group can’t see them. I’ve seen it many times as I’ve approached them. You know you’ve taken a step too far when the tail goes up, even if the deer doesn’t immediately run away.

The consensus now is that this flashy signal is for the predator, not other deer. But, why wave a white flag when you could be better off blending into the background? Deer flag most often when they’re out in the open and when you are still a good ways off. It’s essentially their way of telling the predator (or you) that they’ve spotted the danger and are prepared to outrun it.

The hard part is figuring out how predators respond to such a signal. Humans and domestic dogs don’t understand the language and are poor models of how a coyote or wolf might behave. No one has managed to collect data on how natural predators respond to flagging However, deer aren’t the only animals to use an ‘I see you’ signal when they’ve spotted a predator.

Many ungulates, like Thomson’s gazelles, pronghorn, and springbok will leap from all four feet, straight up into the air, in a behaviour called stotting, when they spot an approaching predator. Like flagging, this jump signals to the predator that its been seen, then takes it one step further by also communicating that they are more than capable of outrunning the threat.  It seems to work. Studies in Africa have found that cheetahs will abandon hunts more frequently when their target stots and if they still choose to initiate a chase, they’re less likely to win.

Like with most animals, these relatively simple signals are just a small part of a whole array of behaviours that make up a complex web of communication between predator and prey. So, take the time to be observant. With patience and intuition, you can learn the language and open your eyes to a whole new level of understanding of the world around you.

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.

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.

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.

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.

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.