January 2010 – Seabrooke Leckie

Coleopteran art work

A couple of weeks ago, while out hiking the 100-acre woods, I discovered this well-engraved tree when wandering about the forest off-trail. Dead tress that have lost their bark are not an uncommon sight in a mature forest. Sometimes the cause of death isn’t clear, for instance if the tree was killed by disease or defoliation. However, trees that are killed by engraver beetles, members of the subfamily Scolytinae (interestingly, now considered to be a member of the family Curculionidae, the true weevils), leave clear evidence of their past presence. The galleries carved into the bark by the larvae as they feed are often quite intricate, and give the group their common name.

The galleries on this tree caught my eye both because they were dark, and so stood out from the pale-coloured trunk, but also because they were all perfectly horizontal. Also interesting to note was that they were all on the north side of the tree. I assume this had something to do with either light-avoidance or heat-avoidance, since the tree stood near the edge of the woods and its south side would have been warmed by the sun.

Quite often you can identify the species that made the engravings by the patterns of the tunnels. The only species that made horizontal galleries that I could find mention of online was the Fir Engraver, Scolytus ventralis. The site that I initially found the info at said, “The gallery pattern of the fir engraver is unique” and “distinct gallery pattern … distinguishes it from associates”, a statement that was repeated on a couple of other pages.

This one was for the Rocky Mountains. I tried to find any mention of the species, or any other species that made horizontal galleries, in Ontario or the east, but didn’t turn up anything. So much logging is done in western North America that a great deal of literature exists for forestry pests on that side of the continent. So I’m working on the assumption that this is the work of a Fir Engraver, and that the dead tree is therefore a fir. Despite the fact that this pdf says they’re only found as far east as the Rocky Mountains. Any eastern folks know an alternative ID, or perhaps a good reference to engraver galleries for this region?

Edit: Upon following a link to a government website for reporting exotic fauna, left me by a commenter, below, I discovered some information on the native elm bark beetle, Hylurgopinus rufipes (that’s the beetle that’s native, though I suppose the elms are also native). This is the species native to the east that creates horizontal galleries, so these photos are almost undoubtedly of elm bark beetles. The adults feed on the soft bark of young twigs on healthy trees, prior to mating and laying eggs, and are one of the primary vectors of Dutch Elm Disease as individuals move from one tree to another during their foraging, picking up the fungus from infected trees, and infecting healthy ones when they’re feeding, in areas where the disease is present. The info page notes that it’s the disease, not the beetle itself, that usually kills the trees, since females usually seek out already dead or dying elms in which to lay their eggs. Whether this elm died from DED or some other cause I cannot say.

The thick horizontal line was bored by the parent beetles. The adults both work on the tunnel, with one boring first and creating a mating chamber. The female bores away from the chamber after mating, laying her eggs along the sides of the tunnel. In the case of the Fir Engraver, she bores across the grain of the wood. Females of other species will bore with the grain of the wood, or at random. When the eggs hatch the larvae tunnel perpendicular to the female’s tunnel, creating the pattern seen here. The larvae’s tunnels end when the grubs get large enough to pupate. They overwinter as larvae, finish growing in the spring, and then pupate and emerge in early summer.

Tay Meadows Tidbit – Resilience

While walking through the cedar woods at the back of the property last week, I came across this oddly-shapen poplar tree. Being so used to the idea that trees grow vertically, any trunk that crosses that pattern really stands out. What was particularly interesting to me about this tree was the curve in the middle. How would that have happened? It’s almost as though the trunk was made of plasticine and sagged once it was horizontal.

You can’t really see it in this photo, too many trees in the way, but the branches at the top of the tree curve up from the trunk and are growing vertically, suggesting that the tree, despite the big split in its trunk, is still alive. So my first thought was that this happened when it was still shorter, and the stuff to the right of the big curve has grown since. But that doesn’t make sense, either, because the tip should have started growing straight up again at the point where it found itself horizontal, which would have been the low point on the curve in that case.

Looking more closely at the trunk, it would appear that this isn’t the first time this poor tree got broken. There’s the fresh snap, still looking a little raw and coloured, at the far left. Then, just a short distance to the right of it, is a jagged bit of wood sticking out from the line of the trunk. It looks like some years ago the trunk snapped at that point, but not completely. Cause is hard to say, being an old injury. The top part of the tree toppled to the side, but was still affixed enough to keep growing. It did, at that point, turn to start growing straight up, and it probably lasted that way many years, given the thickness of the trunk and how much tree is grown from the point where the trunk makes a right-turn (see image below). This old break might have happened in two stages, a small tear first that caused the initial swooping shape, and the second, larger rip that resulted in an abrupt right-turn as the tip corrected for its new orientation.

Perhaps, eventually, the top part of the tree, growing sideways from the trunk base, grew too heavy to continue to be supported, and the trunk broke a second time. Given the vertical growth of the branches at the top of the tree, this second break didn’t kill it, either. What amazing resilience.

Resilient tree, pre-break — My crude reconstruction of the tree before the most recent break, but after the first (simply rotated the top half of the tree in Photoshop so it'd line up with the base of the trunk).

Wandering winter waxwings

I went out late to take Raven for her afternoon walk today. It was nearly four by the time I finally got the skis strapped on (with the mild weather, all the snow was wet and stuck to the snowshoes when I hiked out, making my feet feel uncomfortably heavy). The skis make more noise than the snowshoes, and I had to watch where I was going because the trail out had gotten a little rough with the melt and certain un-snowshoed travelers making holes in the track. So I was nearly halfway out along the first field before the sound of the birds registered. I stopped, looked up. And there, at the top of the trees just ahead, was a huge flock of Bohemian Waxwings, all chirring in their high-pitched bell-like call. I hadn’t brought my camera. I hadn’t even brought my binoculars, figuring it was so late in the day. What to do?

I struggled only a moment before turning back and skiing as fast as my clumsy rustiness and bumpy trail would let me, glancing once or twice over my shoulder to make sure they hadn’t flown. The way I figured it, if they flew before I came back out with the camera, I hadn’t lost anything, but I most definitely would not be getting a photo if I didn’t go back for it. I grabbed the camera, switched out the lenses to the telephoto, called in to Dan that there was a flock of Bohemians (“How many?” “Oh, dunno… twenty? Twenty-five? Fairly large.”), hurried back out, strapped on the skis again, and started back down the trail.

They’d stayed. Whew! Thank you, birdies! I would’ve been disappointed not to get a photo, but not upset; it was a thrill just to discover them. I realized on going back out that the group was larger than my initial hurried estimate. In fact, when I sat down to count the individuals in the top photo of this post, I came up with a total of 85 birds. That’s a pretty good-sized flock!

I can count on one hand the number of times I’d seen Bohemians prior to this (twice). They’re an irruptive species that breeds in the far north, from the Hudson Bay of Northern Ontario, west through the boreal into Alaska, and south through the Rockies to about the Canada-US border. The closest breeding population of Bohemian Waxwings to us here in eastern Ontario would be the Hudson Bay population, some 1200 km (700 miles) away as the waxwing flies, and even there their numbers are thin.

In the recent Ontario Breeding Bird Atlas the species was detected in just 16 of about 85 100-square-km squares surveyed, with a probability of observation of just 6% (that is, the percent chance that you’ll detect the species in any given square in the region within the first 20 hours of field work – the method of data standardization used in the atlas). The first documented nest of the species in Ontario was only found in 2003.

Bohemian Waxwings feed primarily on mountain-ash berries in the winter. When crops of these berries are good in the north they rarely roam very far south. However, when crops are poor they may travel farther in search of food. Ontario birder Ron Pittaway writes a “winter finch forecast” every year where he consults naturalists from across Ontario and other parts of the country to assess tree seed crops in various regions. Knowing how food supplies are distributed about the northern forests helps him to make a prediction on what northern species might irrupt south and in what numbers. He’s usually pretty accurate. This year he indicated that mountain-ash berries are in good supply through much of the north, and so there will be low numbers coming south this year.

He also notes that while spruce, hemlock and birch crops are poor in northeastern Ontario, they’re good in northwestern Ontario and crossbills and redpolls will mostly move in that direction rather than come south this year. I haven’t seen a single redpoll yet this winter.

Slightly larger than Cedar Waxwings, they can easily be told apart by their grayer bellies and rufous undertail coverts. This is good, because when you’re looking up at a group of waxwings perched at the top of a tree, it’s often hard to see the other diagnostic marking, the white-and-yellow patterns on the wings. I pished to try to draw them down a bit closer, but they just tipped their heads and laughed at me. Yeah right, they seemed to say, we saw you walk up here, and your black wolf isn’t helping make you any more convincing.

They hung around just long enough for me to run off a couple dozen shots, and then, in one decisive movement, they all took off and departed for places west. I was pretty surprised to see them in the first place, really. Neither the 30 acres behind the house or the 100-acre woods down the road have much in the way of berry bushes, that I’ve seen, and even early on in the winter I’d noted to myself that we probably wouldn’t be seeing any waxwings as a result. So I was delighted they decided to swing by to say hello!

"Bohemian Waxwing / Jaseur boreal" by Eric Bégin on Flickr -- A closer encounter than mine! Taken in Québec last April.

Hare highway

Through the cedar forests at the back of our main property, as well as the coniferous stands over at the 100-acre woods, there is always an abundance of lagomorph (rabbits and hares) tracks. In areas thick with conifers that have more open understories the tracks are everywhere, criss-crossing back and forth. It’s funny the difference in bunny tracks between the last house and this; while at the lake I never saw a rabbit, and very rarely saw tracks, here the distinctive T-shaped tracks are everywhere.

They’re huge, compared to what I’m used to seeing, too. Those back paws (top prints, because the animal lands first with its front paws and then extends and places its back paws in front of them for the next bound) are a good 4-5 inches (10-12 cm) long. I’m fairly certain that these are Snowshoe Hare tracks. Back in the fall I glimpsed a white rabbit disappearing into the bushes at the 100-acre woods. Since I’m pretty sure I hadn’t fallen into Wonderland, the only white lagomorph around here is the Snowshoe Hare, which can start changing coats as early as September. Snowshoe Hares are about the same size and weight as Eastern Cottontails, but they have proportionally bigger (much bigger!) feet. The two species overlap in range a little (as in Ontario), but generally speaking the Snowshoe is a northern species while the Cottontail is southern. The Snowshoe’s oversized feet are an adaptation to winters with regular, heavy snowfall. When the snow is loose, the hare will spread its toes out for an even greater surface area.

Often in the areas scattered with prints there is a single, well-used trail that runs through the whole area. This is a behaviour unique to Snowshoes, not seen in Cottontails. The trails generally run between favoured foraging areas and resting sites or burrows. They’re usually called runways, but I call them the hare highways. The hares use these routes in both winter and summer (though of course they’re only really observable when there’s snow on the ground). They keep them well-maintained, nipping back encroaching vegetation with their teeth. The highways serve as emergency escape routes as well, so it pays to keep them clear of obstacles. I’ve never seen the trails being used; aside from that brief white flash in the fall, I’ve never seen a hare. Generally speaking they do most of their foraging and other activity at night, perhaps to avoid day-hunting hawks. Probably if I followed one of these highways to its end I might find the hare’s daytime resting location.

I’ve noticed that in areas well-frequented by the hares there are often orange patches in the snow. At first I was writing these off as sap stains from overhanging trees, but when I started paying more attention I noticed they only occurred around the tracks. Even closer attention revealed that some stains had a hole in the middle. They are, as I’m sure you’ve guessed, urine stains from the Snowshoe Hares. According to a number of websites I found, the orange urine is also characteristic of the Snowshoe. Its colour is probably due to the large quantity of conifer leaves/needles that the hares eat as part of their winter diet. While both Snowshoes and Cottontails will eat bark and twigs, I believe only the hares will also feed on needles. The needles contain chlorophyll, which in turn contains a type of molecule called porphyrin, also found in haemoglobin and what gives blood its red colour. This is excreted in the hare’s urine. Of course, this isn’t the only reason for orange urine, and neither does it completely eliminate Cottontails from also producing orange urine, but it’s apparently the general trend. Combined with the tracks and the hare highways, it’s a pretty good indication.

So understanding that that’s what the orange stains are – what the heck was going on here? I found this under a pine in an area frequented by Snowshoes. I noticed there were two colours of droppings in the area (below), which would likely indicate either one hare that had eaten two meals of different composition, or two hares using the same area. The arcs of urine on the left suggest that the hare peed as its butt swung around (if it was peeing as it hopped straight forward, one would expect the line of urine would be straight). My first thought was two hares fighting, circling around each other or flopping around as they scrabbled. But there’s no evidence of conflict, the snow in the area appears undisturbed but for the stains and a few normal tracks. Also, there’s that big pine branch at the side that would get in the way while fighting and would probably show broken bits if it were run into. Though each hare has a 7 to 17 acre home range it stays in and ranges often overlap, I haven’t found anything that suggests they’re territorial such that this might be some sort of territory marking. And females don’t come into estrus until March, so it’s much too early for this to be related to mating behaviour. So I’m left scratching my head over this one.

Tay Meadows Tidbit – Ctenucha caterpillar

On the same day that I found the pile of feathers at the Perth Wildlife Refuge, my mom and I also came across another surprising discovery. Caught in a pawprint in the snow, at the edge of the path where it crossed through an open field section, was a caterpillar. It was a moderately warm day, by winter standards, about 6°C (43°F), but even still – a caterpillar? What was it thinking? No matter how nice and warm that sun felt on its back, surely the snow must have felt cold under its tiny tootsies. By the time we happened across it it was late in the afternoon and the sun was sinking, no longer providing the sort of warmth it would have at midday. The caterpillar was sluggish, but still alive. I took a few photos of it on my palm, where perhaps the heat of my hand helped to revive it a little. Then I found a clump of grass under a branch that seemed fairly protected and tucked the caterpillar in there.

The fuzziness of it means it’s most likely in the tiger moth family, Arctiidae, and I assumed that the individual tufts along the back suggested tussock moth (of the Tribe Phaegopterini). I browsed through BugGuide’s Phaegopterini pages, but didn’t see anything that was a perfect match. The closest was Silver-spotted Tiger Moth, I think. I submitted it to the ID request pages to get a confirmation or a correction on ID. Turned out that I was right on the family, but wrong on the tribe. The caterpillar was identified for me as likely a Virginia Ctenucha, Ctenucha virginica, which is in the Tribe Ctenuchini. Virginia Ctenuchas are a meadow species, with the caterpillar feeding on grasses, sedges, etc. The caterpillars overwinter at the ground surface, underneath leaf litter or matted-down grass. Perhaps this one had been near a rock or some object that had warmed substantially more than the surrounding ground, melting enough of a hole to expose the grasses and warm the spot where it was hiding.