The Marvelous in Nature

Sunscreen for new leaves

Dutchman's Breeches plantlet

One of the nice things about having kept a blog for multiple years is that you can go back to the same time for previous years to see what was happening back then, or to find out when a particular sighting occurred. I was curious about the timing of the wildflowers for the last couple of years, given how delayed things have been this year due to the cold. Last year, the very first of the Dutchman’s Breeches were just starting to bloom on April 8. The year before that, 2009, I first noticed them on April 17; but nearly every plant was in full bloom by that time, so the first one had probably opened a week earlier – which would work out to roughly the same timing.

With those dates in mind, I visited the spot in our woods here where we have a large concentration of the plants, to see how they were coming along. I expected that everything was going to be slow, so I wasn’t surprised to see that the plants were still small, just beginning to unfurl their leaves, when I looked on April 8. A while yet before they’ll be blooming. Still, I was pleased to see them coming up; I’d been there a week earlier to look and had found nothing yet.

Dutchman's Breeches plantlet

It’s interesting that the early leaves are tinged in red, when the mature plant is fully green (albeit with reddish stems). Turns out this has an adaptive function. The red colour is due to the presence of anthocyanins, the same pigment found in red autumn leaves. The pigments serve as a sort of sunscreen for these young and sensitive leaves, protecting them from burning. Not surprisingly, perhaps, this trait is most often seen in plants that spend much or most of their life in the shade. For spring ephemerals like the Dutchman’s Breeches, the early spring sunlight, before the leaves have appeared on the trees to shade the forest floor, is relatively strong. As the leaves grow and mature, and become gradually hardier, the red pigments are slowly lost, allowing the leaves to acclimate to the light of the sun.

There have been a few scientific studies testing this hypothesis. As someone who went through school for science and, with much relief, abandoned academia, I often find the cumbersome technicality of scientific language such as this amusing: “[The presence of anthocyanins] may compensate for a low capacity in the xanthophyll cycle-dependent harmless dissipation of excess excitation energy.” Or, you know, the inability of the leaves to handle extra sunlight without burning. They haven’t worked up their tan yet.

Jack with Dutchman's Breeches plantlets

I’ll close with a couple of photos of the dogs. As regular readers of the blog will know, I like to pose Raven next to things for a scale reference. At two-and-a-half years old, she’s well-trained and obedient, quiet and patient (usually. Unless water or chipmunks are involved). Jack, however, is still just learning. Patience is not his strong suite. So I get in a bit of practice where I can. We’re getting there.

The plants are (were) still so small that you can barely even notice them in Raven’s photo, but Jack’s still small enough to make a better scale reference.

Raven with Dutchman's Breeches plantlets

Daytime bat

Swamp

For some reason, I don’t know why, I managed to remain completely clueless about the existence of Chorus Frogs (Pseudacris triseriata) until a couple of years ago, and I only actually figured out what they sound like last night. This might be excused if I had no knowledge of any of the frogs or their calls, but I grew up beside a swamp; Spring Peepers, American Toads, Wood Frogs and Gray Treefrogs were all a much-anticipated part of spring. I would fall asleep at night with my window cracked open, listening to the (sometimes very loud) choir from the swamp. And yet, for some inexplicable reason, I never picked up on Chorus Frogs. It’s not even like they lack a distinct voice; when I listened to the recordings last night, I surprised myself in saying “I know that! I could swear I grew up hearing that in our swamp.”

So when I heard some this afternoon, calling from some wetland over in the neighbour’s woods, I decided to grab my camera and go check it out. It was a gorgeous day and I was looking for an excuse not to go back inside; maybe, if I was lucky, I could spot one. I made the mistake of letting Raven tag along, however. She was already outside, and though it did cross my mind that she might be a little disruptive, I thought I could just have her sit-stay by the water while I poked around. I’d forgotten how much fun she has in water, and she hasn’t really seen much water since last fall. So when we got there, it was just too much. She tried her best, she really did; she sat-stayed for as long as her quivering muscles would let her. And then she couldn’t hold herself back any longer, and leapt into the water, tuning out all attempts by me to call her back (which, really, is rather ineffectual unless you’ve got one of those remote-controlled collars on them that’ll vibrate when you press a button. Otherwise, what do they care if you yell?).

So the frogs didn’t happen. I could hear them, but I had trouble getting close enough to any to even have a chance of seeing one, since inevitably Raven would bound through just as I thought I might be getting closeish to one. But I found something just as good, or even better.

brown bat, prob. Myotis sp.

I didn’t notice it at first, until it left the tree it had been hanging on on one of Raven’s drive-bys. It was a bat. It swooped down toward the water’s surface, skimming along and touching down once or twice, scooping insects from its surface (presumably; possibly it might have been drinking, although these shots suggest a different posture for that). Then it would return to the tree trunk to eat, hanging upside-down.

I was absolutely fascinated, and this made the entire trek worthwhile. I’m not sure how long I stood there, watching it, but probably fifteen or twenty minutes. It moved to the far side of the swamp for a little bit, and I watched it fly back and forth over the water over there, while a Hairy Woodpecker worked a tree and a couple of robins moved through the branches above.

(Naturally, I didn’t have my telephoto lens, but at least I had my mid-sized lens, my 100mm, and not my short landscape lens, the 55mm. These are all 100% crops, which, in combination with the moving target, accounts for the low image quality.)

brown bat, prob. Myotis sp.

I was standing at the northeast side of the water, so as it swooped back and forth the sun would shine through its thin wing membrane, illuminating it and highlighting the bone structure. That’s not something you get to see too often!

I was a little surprised to see a bat out in plain daylight, and in the sun, no less, not even the deep shade of the forest (or what might pass for deep shade in the leafless deciduous woods). Googling it, though, it seems this isn’t an altogether unusual occurrence. Most of our bats hibernate over the winter. In the spring, as the temperatures are just starting to rise, the nights can often still be quite cool or even freezing, even while the days are fairly warm. Early-risers may take advantage of these warmer daytime temperatures to do some foraging, choosing to sleep at night instead, at least until the nights start to warm up, too. Not only are there a lot more insects out flying during the day (if the temperature’s really cold, there might not be any insects at all at night), but it’s a lot easier on the bat, too. Once the nights are warm enough they’ll return to their nocturnal habits.

brown bat, prob. Myotis sp.

I couldn’t tell you what species it was. According to the Atlas of the Mammals of Ontario, there are 8 species of bat in the province. I know Red Bat (Lasiurus borealis), Silver-haired Bat (Lasionycteris noctivagans) and Hoary Bat (Lasiurus cinereus), but the rest of Ontario’s bats all sort of blend in together – especially when you’re seeing them from a slight distance, while they’re on the wing. The remaining possibilities are Eastern Small-footed Bat (Myotis leibii), Little Brown Bat (Myotis lucifuga), Northern Long-eared Bat (aka Northern Myotis; Myotis septentrionalis), Eastern Pipistrelle (Pipistrellus subflavus), and Big Brown Bat (Eptesicus fuscus). From what I can tell, ID between these species depends primarily on structural details of the ears and head that can’t be seen in flight or from a distance (unless you have a really good camera).

brown bat, prob. Myotis sp.

The two brown bats are the most common, judging from the mammal atlas, and the Big Brown in particular. I read through all of the descriptions in my Peterson mammal guide, though, just in case it offered any clues there. It was the habitat and habits I was most interested in. The habits of Eastern Small-footed Bat and Northern Myotis didn’t seem to match, but the other three had possible similarities:

For Little Brown, it comments: “Forests and rural areas, usually near streams and lakes” and “Emerges at dusk or later, usually flying to water to forage and drink. … Feeds mainly on emerging aquatic insects”.

For Eastern Pipistrelle: “Woodland or mixed farmland” and “Feeds on tiny flies and beetles, hunting over water or at forest edge”.

And for Big Brown: “Forests, farms, cities” and “Feeds on beetles and other insects, hunting over fields or streams … Will awake and become active in response to temperature change – a bat seen out and about in midwinter is almost sure to be this species.”

brown bat, prob. Myotis sp.

It’s the note about Little Brown feeding on emerging aquatic insects that causes me to lean toward that species as the most likely candidate, although Big Brown seems like a pretty good possibility as well. Being completely subjective about it, the shape and relative size of the head in the first photo, where it’s hanging on the tree, seem a better match for the Little Brown in my guide. But it’s probably one of those things that has to be left without a definitive ID. Pretty cool, regardless!

brown bat, prob. Myotis sp.

Two curious trees

Path of lightning strike

That is to say, two strange and interesting trees (I doubt the trees feel all that much curiosity, although we do suffer from something of a language barrier, so who’s to say, really; it’s probably a little presumptuous of us to think we know what they’re feeling). I spotted this first tree the same day I returned to the beetle-hole-turned-sapsucker-well grove over at the 100-acre woods; it was the subject of my pushed-luck photos, the ones I managed to take following the resurrection of my camera battery. I wouldn’t’ve been heartbroken had the battery returned to the dead and I’d been forced to return home without the photos, but I did stop and puzzle over what I was seeing for a few minutes.

What caught my eye, initially, was this ridge that seemed to run along the side of the trunk. It was about two inches wide and nearly the same high, sticking out from the trunk proper. It looked an awful lot like the thick trunk of an ancient climbing vine, a Virginia Creeper or grapevine (our Poison Ivy doesn’t climb here). It took close examination to convince me that it wasn’t external to the tree (or previously-external-but-now-being-grown-over). No, it actually appeared to be an old wound, now healed and thick with scar tissue. The fact that the ridge broke and jumped slightly sideways at eye-level confirmed that it wasn’t (or hadn’t been) a vine.

Intrigued and still puzzled, I circled the tree and followed the ridge as it rose up the length of the trunk – in a spiral, all the way up to where the branches started, thirty or forty feet from the ground. Any guesses?

Twisting path of lightning strike

I believe this is the scar left from a lightning strike many years ago. I wrote a whole post about how lighting works a few years ago (I initially wrote a couple, and then realized it had been longer than that; I’ve been blogging more than three years. Goodness.), after a tree behind my parents’ house had been hit and destroyed by a strike. Trees are often hit by lightning not just because they’re tall, but also because they’re wet – whether on the outside, from rain, or the inside, from sap – and therefore conduct electricity extremely well. The lightning, once it reaches the tree, takes the path of least resistance. Although this can sometimes be down inside the heart of the tree (as it was for the pine), usually with disastrous results, it can also (perhaps more often) be down the outside of the tree, either through the water that’s soaked the outer bark, or through the sapwood just under the bark.

While lightning traveling the outside of the tree will likely do little damage beyond superficial burns, if the electricity enters the tree it can be more problematic. Lightning is incredibly hot, even hotter than the surface of the sun (which means little to most of us, since none of us have been there to experience it firsthand, but does at least give you the understanding that lightning is really, really hot). It should come as no surprise that any liquid that comes in contact with lightning is instantly vapourized. When the lightning travels through the inside of the tree, through the sap, the sap is instantly vapourized, turned into a gas. Gas takes up more space than liquid – it’s all the same atoms, just spaced a whole lot farther apart (yes, you can have solid/frozen oxygen, if you can somehow get the temperature down to −362°F/−219°C) – so you can imagine what effect this has if the liquid had been in a confined space. Yup, that’s right: kaboom.

If the lightning travels through the outer sapwood, rather than down through the heart of the tree, the effect is the same, but less pronounced. The outer bark and probably the layers of sapwood (the phloem and xylem) will be stripped along the route the lightning takes, but the rest of the tree will remain intact. As the tree heals over the open wound, it will inevitably form a ridge of scar tissue, and that’s what I think I was seeing here.

Dead tree with twsting wood pattern

Why the spiral, though? Well, although we can’t often tell from the outside, under the thick outer bark the inner wood of the tree is sometimes slightly twisted. It’s easiest to see this on dead trees where the outer bark has all sloughed off over time. This is such a one that I found last fall, for instance. I’m not sure what caused the two wood colours, but it does help to make the twists and waves of the trunk pretty obvious. As you can see, the wood doesn’t necessarily grow straight. Some trees have a very pronounced spiral. (I do actually have photos – somewhere – of such a dead trunk, but don’t ask me to find them.)

So what I think happened, why I think the lightning traced a spiral route down the tree, is it was simply following the path of the bark. Pretty neat. The tree seems to be doing well these days, despite the incident.

Broken and healed limb, pine tree

This tree I’ve seen a few times. It’s also over at the 100-acre woods, but at the edge of one of the fields. I’ve walked by it a number of times, and when I photographed it a couple of days ago, it wasn’t the first time I’d noticed it. In fact, I think the first time I’d consciously taken note of it was during the winter; this year or last, I can’t remember. I do remember, however, thinking that the branch had been torn in one of our ice storms. Pines seem particularly susceptible to this sort of damage, because they have so many long needles which catch not only ice but snow, and because they’re a softwood, and their limbs aren’t quite as sturdy as, say, a maple or oak.

So I’d noticed it before and not thought too much of it, but when I walked by the other day I realized two things: first, the limb was still alive, and second, that it wasn’t even a recent, open wound. Looking more closely (below) it’s obvious that this happened quite some time ago. Not only is there no recent wound, there’s barely any evidence of a wound at all. Like the lightning-struck tree, the damage was minimal; the pine’s limb was still connected by enough tissue that it simply grew over and sealed the wound, and carried on.

I love seeing resiliency in nature.

Broken and healed limb, pine tree

A few more moths

Three-spotted Sallow, Eupsilia tristigmata

It’s been a slow start to the spring. The weather has been cold, cold, cold, rain, rain, and a little bit of snow thrown in there for good measure. Even our sunny days have mostly been cool. We’ve only had a couple of days where I’ve been inclined to go out without a jacket. Fortunately when Dan’s dad was up to visit last week the afternoon happened to be one of our gorgeous days, and we managed to get the gardens all cleared up, between the three of us. I haven’t really had another opportunity since then.

Where I’ve noticed this cold weather most has been in the moths. There just haven’t been any, really. The first moth this year (first macromoth, that is) was really late compared to the last two years (March 17 this year, versus March 8 and 6 in the previous two, respectively). And I didn’t see another macromoth until last night – which, for the record, is now April.

To put this in perspective, by this time (April 5) in 2009 (the only spring where I actually kept count for the first couple months), I had tallied nearly three hundred individuals. This year I have eight macros and perhaps half a dozen micros.

So forgive me if I get a little excited over my handful of moths.

The leading species here is a Three-spotted Sallow, Eupsilia tristigmata. It’s yet another of those early-season Eupsilia species, two of which I’ve already recorded for this year (Morrison’s and Straight-toothed). In fact, I got another Straight-toothed last night, as well, but didn’t feel the need to photograph it. Three-spotted seems to be more common here at this house than it did at the lake house – I got hardly any there, but I catch them regularly here. They look somewhat the same, but the large, dark spot beside the orbicular spot is diagnostic of this species (the Straight-toothed, recall, has the large spot flanked by two tiny white ones).

Aurora Semioscopis, Semioscopis aurorella

The other three moths I have are from the night before. This first one is a semioscopis, the first one I’ve seen this year. The semioscopises (semioscopi?) are gray with longer, somewhat teardrop-shaped wings, and are another of the early-season groups, often one of the first I encounter at the start of the season. This one’s an Aurora Semioscopis, Semioscopis aurorella.

Hasty Acleris, Acleris hastiana

The last two are both the same species, showing slightly different markings: Hasty Acleris, Acleris hastiana. The aclerises are a huge group, many of them confusingly patterned, and can be encountered all year, but a few members of the genus, including this one, overwinter as adults and as such are often one of the first moths encountered in spring.

Their cold-hardiness makes them irritatingly difficult to photograph, however, because your fridge is a rather balmy 4°C, and there’s a good chance you caught them fluttering at the light after the temperature had already dropped to 2°C. The fridge is not going to put them into any serious state of torpor. Even putting them in the freezer, which usually knocks a macromoth into torpor within a couple of minutes, does little for these micromoths. I tend not to get many good photos of them as a result…

I’m ready for the mothing season to begin in earnest any time now. I’d been planning a trip down to the area of our old lake house, where I’d encountered all the Infants (Archiearis infans and Leucobrephos brephoides); that spring they were out and flying by last week of March, but I’m still waiting for appropriate weather this year. Soon, I hope!

Hasty Acleris, Acleris hastiana

Done in by a sapsucker

Sorry to keep you in suspense! Here’s the final photo:

Eastern Hemlock trunk with holes

It was a sapsucker after all.

Of course, you all knew that, didn’t you? If not by the photos/evidence, then simply by the title of yesterday’s post and which way it was clearly going. But still, I was surprised – and relieved, I have to admit – to discover this, some ways up one of the trees. An answer. Classic (to me) sapsucker sign: stacked, rectangular holes.

But that didn’t explain why five trees were absolutely peppered with little holes, as if someone had come out for shotgun practice there. I’ve seen some worked-over trees, but I’ve never seen sapsucker feeding sign like that. Could these be the favoured trees of a pair that nested in the little swampy bit just a couple dozen meters away? Since sapsuckers don’t winter here, and would be unlikely to remain in one spot long enough during migration to create such a multitude of holes, it would have to have been birds present during the summer months.

To try to find an answer, I pulled out the Birds of North America account for Yellow-bellied Sapsucker and began reading. It makes the note that pairs will usually return to the same breeding site as in previous years, and also indicates that the longevity record for a wild bird (these are usually inferred through the time between two captures of a banded bird, whose age was known when it was first banded) is approaching 7 years. So perhaps if the same pair came back to this site for four or five years, they’d have time enough to riddle a few trees.

Fresh sapsucker wells
Active sapsucker wells. I'd forgotten about these photos, which I took a few years ago, back in Toronto.

Something else I came across, though, which I found interesting, and which may also help to explain what I was seeing here: sapsuckers make two types of wells, one that penetrates to the xylem, and the other to the phloem.

Each ring of a tree ring has both xylem and phloem; the xylem is found closer to the center of the tree, while the phloem is found outward, closer to the bark. The xylem is a network of capillary tubes used primarily for the transport of water, and some nutrients, from the roots of the tree to its leaves. Movement of fluids upwards (against gravity) in this network is passive. Water molecules climb the sides of these tiny tubes through capillary action, drawn upward (usually) by transpiration (the tree “breathing”, losing water through its leaves), or sometimes pushed upward by excess water pressure in the root system.

The phloem, the outer layer, transports sugars and other nutrients throughout the plant, to wherever they need to go. Unlike the xylem, which is actual tubes, the phloem is composed of cells, which pass contents from one to another like a bucket brigade. The phloem is where the sap flows, and where the sugar content is highest. The reason that girdling will kill a tree is that with the phloem destroyed all the way around the trunk, the sugars have no way of making it down to the roots to keep the roots alive.

Consider the two systems as your arteries and veins, with the roots as the heart and the leaves as the lungs. The water starts in the roots (your heart) and is pumped up through the tree’s xylem (your arteries) to the leaves (your lungs). There it picks up sugars (oxygen, in this analogy) which it then carries back through the rest of the tree by the phloem (your veins) before returning to the roots to be cycled through again. Of course, this isn’t a perfect analogy because in our bodies the switchover between arteries and veins isn’t at the lungs as I’ve drawn here but at the tissues where the oxygen is dropped off. But you get the idea. Also, just as there remains a small amount of oxygen in the blood that the veins carry back to the heart and lungs, so too is there a little big of sugar in the water going back up from the roots in the xylem.

Yellow-bellied Sapsucker at well
We actually got to see a sapsucker visiting its wells. The one and only time I've observed this behaviour.

Back to the sapsuckers; the wells that they drill into the xylem are circular, usually in horizontal rows of 3 to 15 holes. Those bored into phloem, however, are typically rectangular and stacked vertically for as much as 20 cm (8 in). What I’m used to thinking of as “sapsucker holes” are their phloem wells.

I’m not entirely clear on why they bore two types, but I would guess it has to do with energetics. Although phloem sap contains >10% sucrose and xylem sap only 2-3% (according to the BNA), xylem sap, by virtue of its density/viscosity and its transport method, flows faster. Although the bird may not need to consume as much phloem sap to obtain the same energy, it would need a lot more wells because of the flow rates. (That said, the BNA indicates that sapsuckers will preferentially choose trees with higher sugar content over trees with lower sugar but higher sap flow. Perhaps in the summer, when they don’t want to be flying all over the territory, they settle for the faster-but-lower-sugar xylem sap flow.)

Incidentally, in the spring the tree has no leaves yet, and so the sugar movement is all unidirectional – from the storage location in the roots, up through the xylem to the branches so the tree can use it to start making new leaves. Maple syrup is made from xylem sap. As soon as the leaves start to bud out and begin photosynthesizing, and the phloem sap starts flowing, the taste of the collected sap changes (not for the better) and maple syrup season is over. [In the spirit of full disclosure, I deduced this paragraph from everything I’ve just learned about the two types of sap, except for the bit about maple syrup season ending at leaf out because the taste changes, which I already knew.]

What about why sapsuckers arrange the two types of wells differently? This, too, isn’t specifically stated in the BNA account but I have a guess. Because the xylem operates passively, putting a second well above the first does you no good – the sap would leak out at the first well it gets to and the well above wouldn’t function. So they put them side-by-side. They could also do this with the phloem wells, and you do sometimes see multiple stacks of phloem wells side-by-side. But (and here the BNA account does say) sugars tend to back up in the phloem above a wound/well where the transport cells have been damaged (remember, they’re headed down toward the roots, so they accumulate above the well), so when the first well starts to seal up, the sapsuckers drill their second well above it, where the sugars have become concentrated.

I feel I’ve learned a lesson here. (Ironic, because I’m usually pretty careful about double-checking my info, or using language such as “probably”, “might be”, or “I think” if I’m not thoroughly certain.) Hopefully you have, too, and without having had to eat your words! Still, I feel it was a worthwhile lesson, to have learned that cool stuff about sapsucker wells.