The Marvelous in Nature

The February freeze

It was minus frigid today. The thermometer showed a high of -8 oC (18 oF) in the afternoon, and a brisk wind dropped it to the teens. Actually, that’s not terribly cold; yesterday it was -17 oC (0 oF), with a wind chill of -29 oC (-20 oF). I had the pleasure of walking home from the subway in that, and the bits of my face that were exposed, my cheekbones and the bridge of my nose, were aching by the time I got inside. The ten minute walk probably only took me seven because I was hurrying so much! The good news was that my new down jacket performed fabulously in its first serious field test. Average temperatures for this time of year run about -1 oC according to weather.ca, so we’re in a bit of a cold snap.

Today, back out in the country at my parents’, I couldn’t help but think of all the little critters who didn’t have the ability to hide indoors beside the wood stove. Those juncos looked a little cold out there. They turned down my offer to come in, though. A lot of animals suffer through conditions that would freeze us solid quickly. All those poor male Emperor Penguins incubating their eggs in the Antarctic winter (seen March of the Penguins?) comes to mind. More locally, the chickadees and sparrows in the backyard often make it through long stretches of sub-freezing temperatures and deep snow.

One of the keys to their survival is their full-body down jackets (or, in the case of mammals, fur coats) that keep them well-insulated. I reflected, as I was hurrying down the street yesterday, that if I had a down jacket for my legs and face I’d be in pretty good shape, since my torso was quite comfy. Part of that was the fact that I was being quite active and producing a lot of heat. This is also a key for birds; they keep relatively active during the day, and the heat they produce then gets trapped under the layers of down. On the above feather, the fluffy bit at the bottom creates many tiny air pockets that trap warm air against the body (this is the bit they stuff in your down jacket or duvet, though less expensive ones include the whole feather), while the smooth upper part streamlines the bird’s body to optimize aerodynamics. Mammals have a similar system of hairs that creates the same effect. Both birds and mammals have the ability, through itty-bitty muscles at the base of the feather/hair, to raise the insulative layer to create a wider air pocket and trap more heat when it’s colder (this is what goosebumps are… we don’t have enough hair for it to do much, though).

But what about those tiny bare feet? Standing on the snow in the winter it would be hard to keep any warmth in them at all. And think of the ducks swimming on the near-freezing water. Well, as the junco above is demonstrating, often birds will tuck one foot up into their breast feathers if they’re resting (I’ve even seen some birds continue to forage for a time, hopping on one foot, while the other’s tucked up). Ducks, gulls and other waterbirds do this frequently, landbirds are less often observed doing it (mostly because they don’t loaf as much as gulls do!).

In addition to that, they’ve evolved an ingenious circulatory system to their legs, called countercurrent circulation. The arteries in their legs line up right next to the veins, so that the blood being pumped down into the legs through the arteries transfers its heat to the blood coming back up from the feet in the veins. This cools the blood down before reaching the feet to minimize heat loss to the environment, and warms it back up before it reenters the body. There’s actually very little tissue in a bird’s foot, it’s mostly tendons, so it doesn’t have the same heat requirements that muscle or organs do (in fact, it can approach freezing with no serious consequences). Mammals have a similar system in their legs, although they have more muscle tissue, so also use a layer of fur for insulation.

Speaking of mammals… look who was out today! I have seen the Red Squirrel more this winter than I can recall in previous years. I have a feeling it’s in part because he’s set up shop in the attic of the house, I think in the area over the room with the wood stove. Judging by the size of the icicles hanging off the eaves there, the attic is probably pretty warm, and I imagine he doesn’t have to work too hard to conserve heat. Plus, with the feeders right there and handy for him, once his cache ran low he didn’t have to go too far for more food. I may have seen more of him this winter than the Gray Squirrels – unusual.

“Oh my GOSH it’s cold!”

The Black Knot

Edit: This post was recently included in the March edition of the Festival of Trees, a blog carnival focusing on, you guessed it, trees. You can check out the full edition at Orchards Forever.

There is a bush in the backyard, behind the house, growing beside a large stump. The stump is what remains of a mature pine that came down before I was around, struck by lightning. The shrub and stump were a play-spot for my sisters and I when we were young, and I remember picking blackcaps from the canes that grew under its branches.

In recent winters I’ve noticed a few black, crusty growths forming on some of the small branches. It’s a familiar phenomenon, but one I hadn’t investigated before. When I was much younger we had a plum and a cherry tree on the property, and I recall plucking ripe plums from the branches of the one, and my parents complaining (good-naturedly) about the birds eating the fruit from the other. Both gradually succumbed to a crusty black fungus, and while the cherry struggles on, the plum long ago died and came down (although I did notice a hopeful new sapling right beside where it used to be).

So to see these growths forming on another tree I knew as a kid, I thought I’d investigate. Turns out, it’s fairly common. It’s a fungus, Apiosporina morbosum, known by the common name “the Black Knot” (which sounds rather dramatic). It almost exclusively infects trees of the genus Prunus, which includes cultivated species such as plum or cherry, or wild native species such as chokecherry or black cherry. The little shrub in the backyard is a chokecherry.

This little tree, although I didn’t try to identify it, is probably a black cherry, the most common Prunus species in these woods. It has a substantially more progressed infection. The fungal spores infect the young buds of the tree when it’s just leafing out in the spring, and it takes a few months for the infection to appear. Initially just look like thick brown galls. Eventually, the following spring or summer, the bark splits and the gall turns into these charcoal-black, crusty growths.

The fungal growths are most often seen on smaller branches, but like in the above photo, can sometimes spread to the trunk of the tree. Although an infection on a branch can compromise the branch’s growth and create disfiguring contortions (such as the first photo), it only kills the branch if the growth completely encircles it (called “girdling”). Any portion of the branch above the fungus will die. If the fungus girdles the trunk of the tree, the whole tree will die. The fungus will continue to spread over many years, and eventually will either compromise the tree so severely it will die, or girdles the trunk causing death.

The fungal spores are released by splashing rain and carried by the wind, and mild spells during the spring rains trigger their production and release. Once a tree’s infected, an individual growth will only live a couple years (after which it dies and turns whiteish-pink, colonized by another species of fungus), but during that time it has the ability to spread to other areas of the tree.

The good news is, you can do something about it if one of the trees in your yard becomes infected. It’s simply a matter of removing the infected bit, cutting back to 10 or 20 cm below the infected bit (since the fungus travels under the bark and may be present outside of the growth). This is best done in the winter while the tree and fungus are both dormant, and the fungus should be burned or otherwise disposed of so it doesn’t infect other trees.

So there’s some hope for the little shrub, and perhaps if I prune it this winter I can keep it from spreading to the mature chokecherry that shades the kitchen window. Now just to dig the gardening shears out from where they’ve been packed away for the winter…

Snowstorm, the day after

I took a break this afternoon to wander outside and enjoy the snow of yesterday. It had stopped snowing last night, and the day dawned clear, with a gorgeous blue sky and brilliant sunshine. These are the sorts of days that I love about winter. That, sitting by the fire, and fat softly-falling snowflakes. I could do without the slushy, slippery roads, the freezing rain, the bitterly cold winds (although these are all easier to take while sitting by the fire). The bright white snow and blue sky wonderfully set off the green conifers and red dogwood.

The snow in the front yard was clean and pristine, stretching out beneath the big trees. I can’t bring myself to walk through it, it doesn’t seem right to spoil something so clean and fresh and full of promise. I’ll leave that to the squirrels and rabbits, and I skirt around.

The smooth white of the unbroken snow makes a great canvas, catching the shadows of the big maple above. It seems somewhat abstract, like something that should be hanging in a museum somewhere. Nature is a great artist.

One downside to all this snow is the necessity of clearing it from the driveway so people can come and go. Here a snowball has rolled down off the giant snowbanks created by the plow (they were at least up to my waist in front of the house, and can be larger along the drive). My parents have an old 1945 Ford tractor that my dad has managed to keep running all these years and has hooked a plow to, used primarily in the winter for clearing snow. It’s been a faithful machine, and, given the length of the driveway (see the second photo), let’s hope it continues to be!

All this deep snow can be a challenge to ground-foragers such as the juncos and tree sparrows. At these times feeders become an invaluable resource that allows more birds to survive the harsh weather than might be able to without a supplemental food source. My mom tries her best to keep the feeders stocked through the winter, though wading through knee-deep snow can be a challenge. Certainly appreciated by the birds!

I wasn’t the only one out enjoying the fresh snow. The two younger horses were having a grand old time frolicking in the white stuff, throwing up plumes of it as they raced through. After a few laps around the field they pulled up near the gate where I stood, their bellies caked with snow, their nostrils wide as they panted deeply. But their eyes sparkled with energy and enjoyment.

Mine too.

Noon at night

Last week a big storm system moved through southern Ontario, dumping a pile of snow in its wake. I love being out in the country for snowstorms, both during and after. It doesn’t get much prettier than giant fat snowflakes falling against a backdrop of evergreens and red dogwood. Once the storm has passed the whole world is blanketed in a smooth sheet of pristine white, untouched, as yet, by little feet. All the branches are lined with snow, creating definition among the forest trees.

That night was a full moon, and as I was going to bed I stopped to admire the long shadows of the big maples in the front yard, cast across the sparkling snow. As I often do, I tried to capture the scene with my camera. Although an interesting image, I’m not sure it really did justice to the magical feel of it.

The sky in the picture is pinkish-purple. When I took the picture, standing at the window with the lights off, looking out over the front yard, it was most definitely dark. The above image was shot with a 15 second exposure, enough to try to capture the crispness of the shadows and the brightness of the snow. In using such a long exposure, I also managed to capture some of the ambient light being given off by the town to the south.

It’s called light pollution, and it’s as common and wide-reaching as people are. Although in rural areas, such as my parents’ home, it can be very subtle to discern (most of the time it’s manifested to our eyes as simply a rosy glow along the horizon), in the big city it can be incredibly bright. One lightbulb may not cast a lot of light on its own, but when you combine hundreds of thousands all together… Well, think of it as the difference between the candles on the cake brought in for your niece’s 6th birthday party versus those on your uncle’s 60th. You could probably illuminate the room with your uncle’s cake. The above photo of the city of Toronto, taken from a distance at night, really gives you an idea of the effect. The glow of the lights hangs over the city like a layer of smog.

Today we got another big dump of snow. If you believe what they said on the evening news, it could be record-breaking for amount of snowfall in a single day for the Toronto area (I’m sure places north and west of us would scoff at the paltry amount). It continues to snow even now, having begun before dawn today. It should be done by the time people are heading out to work tomorrow, but it will be a considerable accumulation.

Because it’s still snowing, it’s overcast. Clouds throw another wrench into the mix as far as light pollution goes. The above photo was taken using a similar 15 second exposure as the top photo, pointed out the side window instead of the front, but still generally toward the south. Instead of the pale pinkish-purple sky of the first image, however, we have a deep, vibrant orange. The trees are darker because there was no moon to illuminate them, but the sky is glowing. You can also see the streetlight at the home across the road (private, installed by the homeowners when they first moved to the country, for security I guess; it’s the only one on the street), and a thin ribbon of light as a car drove by during the long exposure (which I think is neat).

Clouds have excellent reflective properties, both of light and of heat, which is why overcast days are often warmer than clear, sunny days. They reflect a lot of the warmth trapped in the atmosphere back down to earth. Similarly, they also reflect a lot of the light cast on them from urban centres. If you’re out walking at night, particularly near town, you’ll find it easier to navigate on overcast nights than on clear ones because of this.

This effect is amplified when you’re inside the light source. Our apartment sits over the garages of the building, and the floodlight illuminating the small parking lot also casts a lot of light on the surroundings. This is particularly noticeable after a good snow, such as in the above photo, taken last week. It can be so bright it almost seems like dawn. The exposure for the above photo was a paltry 1.6 seconds. I started washing the image out if I went any longer than that.

This photo was taken looking south (from the west-facing windows) toward the lake from the apartment. There’s a very noticeable darkness on the horizon over the lake. I suspect (although I don’t know for certain) that this is the delineation between the clouds over the city, casting back all the light, and those over the lake, where there is no light to cast back.

(stars as seen looking lakeward from Tommy Thompson Park on the Toronto lakeshore; long exposure, of course)

When I was a kid I would go out stargazing with my dad, picking out the constellations from the dark starry sky. The big city and neighbouring local towns have all grown since then, and with the increased night light, the stars are fewer and harder to see. This change is noticeable to me, even within my relatively short lifetime, and I find it sad to think of what the sky will be like in another 20 years. When I travelled out to British Columbia a couple years ago, I lived in a small trailer in the bush in the Okanagan Valley. The sky resembled, to quote Incubus, “a backlit canopy with holes punched in it.” It was gorgeous, and something quite unlikely to be seen with any regularity in the Toronto area again.

In summer 2003 the eastern seaboard suffered a “Big Blackout”, and cities were completely darkened, treating their residents to a light show the likes of which probably many of them had never seen. On March 29 this year, at 8pm, Toronto will participate in Earth Hour, a one-hour event where (ideally) the city will turn its lights out on a scale approaching the Big Blackout. The idea behind this is to make a statement to governments and other powers that be on energy usage and climate change, and related environmental issues. Although it’s still a month and a half away, pencil it in on your calendar on March 29 to turn your lights off then head outside to enjoy the sky.

Icicles in reverse

About a year ago, in late winter, Blackburnian called me into the kitchen to show me a bizarre ice cube he’d discovered in the tray in the freezer. It looked like a normal cube, except that at one side, sticking out of the top at a slight angle, was a narrow spike of ice about an inch long. It was the strangest thing, looking a little like the little back-splash of water when a droplet hits the surface, frozen in ice. But obviously that wasn’t possible, so my hypothesis was that a hair had fallen into the cube while it was still liquid, and the water molecules had frozen up its length in a capillary action (where the chemical bonding properties of the water molecule cause it to crawl up a surface a little). Although I could see no hair inside, I’m blonde and figured it was just hidden. After all, what else could cause such a bizarre structure?

This afternoon I opened the freezer door to pull out tonight’s dinner to thaw, and happened to notice a freshly-frozen ice cube tray on the freezer door. And within this tray was – you guessed it – another ice cube spike. Well, what are the odds that another invisible hair had fallen into the cube tray? Particularly since I so rarely fill it, and Blackburnian has dark hair. So this time I did some poking around. Sure enough, it seemed to be a fairly common observation – under the right conditions.

(last year’s ice spike)

Water begins freezing at the edges of its container (the banks of a pond, or the sides of the ice cube tray), where the solid acts as a catalyst (remember the frost?). As the top freezes inward, it creates a little hole in the surface of the ice. At the same time, the ice cube is also freezing along the sides and bottom (doesn’t happen in a pond, but in small, contained bodies of water where the cold reaches all sides, all sides freeze at the same time). Ice is less dense than water, and takes up more space than the water does when it melts. So as the ice cube is freezing from the bottom and sides, the still-unfrozen water inside is getting squeezed out through the hole in the top of the surface.

Like an icicle grows through the addition of more ice as the water droplets running down the outside freeze, so the ice spike grows as more water is pushed up through the hole and freezes at the edges, creating a narrow tube or straw, through which more water is pushed and subsequently freezes. Some ice spikes can grow quite long if the pressure is slow and steady, and the temperatures mild enough to result in slow freezing speeds of the tube. The tube closes off when either the inside of the cube is completely frozen (no more water to force out), the temperature gets too cold (the water on the spike freezes faster than in the cube and seals it off), or the walls of the tube narrow beyond a certain point (where the water coming up forms a bridge between the walls instead of adding to the walls as it freezes).

You’d think that given the nature of an ice cube this ought to be seen more frequently, but it actually takes fairly specific conditions to produce the effect. For one, the water needs to be distilled, or low in dissolved solids (such as salts and minerals, typically found in most well or city water). The salts and minerals in the water will act as a catalyst to freezing so that the ice isn’t growing only from the walls of the tray (and therefore isn’t creating the same pressure on the water inside), although not all of these dissolved solids affect ice formation in the same way. We use a Brita filter, and it’s possible that it had removed enough of the minerals out of these couple ice cubes to encourage the spike to form.

Your freezer also needs to ideally be just below freezing – cool enough to encourage the water to freeze, but not so cold that it will freeze quickly. However, ice spikes will also form under “supercooling” situations, where lukewarm or room-temperature water is placed in a very cold environment (-10 to -20 oC, such as outdoors in winter, or in a freezer, particularly chest freezers which maintain colder temperatures) and is brought to freezing rapidly. In these cases a slightly different sort of ice crystal forms on the surface creating sheets of thin ice, including some that jut into the water below. These crystals, like those in snowflakes, form 60 degree angles creating a triangular opening in the surface, and the sheets hanging into the water form the base of the ice spike as it grows, often resulting in strange angles depending on the way the sheet was hanging.

The Discovery Channel’s show Daily Planet aired a segment a few years ago on the phenomenon after it was sent in by a viewer in Courtenay, BC, who discovered a spike in her birdbath. This site, by Professor Stephen Morris of the University of Toronto, also has a lot of information and links to photos and other sites.

You can try making your own ice spikes simply by freezing distilled water (not tap water!) in an ordinary ice cube tray in your freezer. Good luck and have fun!

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