If a tree falls in the forest


Forests are generally known specifically for their living trees. The tall pillars, their stout trunks reaching for the sky, the branching canopies casting shade on the ground below – they are the very definition of forest, and without them the forest would not exist. And yet, the living trees are only a small part of what forms a forest. Just as vital are the dead trees, the ones still standing as snags and, perhaps more importantly, the ones that have fallen as logs.


Logs play a vital role in the forest ecosystem. As they begin to break down and decompose, they return nutrients back to the soil that may have been locked up in that tree for decades, or even hundreds of years. Because they’re essentially nutrient-rich piles of fertilizer, they provide excellent spots for new life to grow. Often in the tropics, where the majority of the nutrients in the ecosystem are contained within the living matter, fallen trees are swarmed by young plantlings looking for a good start in life. It’s not unusual to have trouble seeing the log for all the little trees and plants growing on it. Such is not usually the case in the temperate north here, but they do still foster growth, often moss or fungus, sometimes ferns or grasses, occasionally young trees.


Rolling a log over can reveal many secrets. They are home to many critters, from vertebrates like salamanders or frogs that hide underneath, to insects and invertebrates that tunnel below or inside. These latter groups are an important part of the decomposition process, breaking it down into pieces that are easier for bacteria and little organisms to digest. The longer a log has been down, the further along the decomposition process as all the little critters get to work. A newly-fallen log is still strong enough to support a person’s weight, but do the same with one that’s been on the ground a number of years and your foot will go right through it. The amount of time it takes for a log to break down completely varies according to the size, density and composition of the wood and the local conditions. Dry and cold conditions tend to slow the decomposition process, as the organisms responsible for much of the cycle are less active, and denser wood will take longer to rot (even within the same tree, sometimes, different densities between the sapwood and the heartwood can create hollow logs, or logs where just the centre remains). A giant red cedar, which has a dense, oily wood, may take a century to completely return to the soil.


I wrote about carpenter ants before, but there are many species of invertebrates that also call dead trees and logs home, and which woodpeckers find tasty. Fallen logs are riddled with woodpecker holes just as often as standing snags are, and it’s not unusual to flush a Pileated or other woodpecker up from what seems like the forest floor. Woodpeckers, and Pileateds specifically, probably help in breaking logs down as they chip pieces off during their excavations. Woodpeckers aren’t the only birds to use logs, though. Ruffed Grouse males will sit atop a large log to perform their drumming displays, where they beat their wings rapidly to create a deep staccato beat, using the log to amplify the sound’s acoustics. Many species of ground-nesting birds will build their nests under the overhang of a fallen log.


Forests go through different stages of maturity, and one of the characteristics of a mature forest is the presence of many fallen logs. A truly mature forest, however, not only has fallen logs, but also has fully decomposed logs. Because the latter no longer look like logs, they can be hard to spot. In walking the woods around here I spent some time searching for a fully-decomposed log to take a photo of, but the forest is too young. I suspect much of the land around here was cleared for farming at one time or another, as there is evidence of split-rail fences that apparently run through the middle of the forest. It could be that the forest in this area is only about 60 or 70 years old. Certainly the really thick, tall, craggy trees that characterize a very old forest are few and far between.

I found a couple that might possibly have been an old log or stump but couldn’t say for sure. The above was one (it’s quite difficult to get a photograph that adequately conveys the sense of a bump in the land, it turns out). These old, decomposed logs show up on the forest floor as raised hummocks. Often they’re long and narrow, much like the log they used to resemble. They can be mistaken for burial mounds, as they have the same sort of formation. Oftentimes you can see two or three trees growing in a line along the hummock, evidence of seedlings that got their start on the decomposing log, now long gone. Because of the amount of time necessary to return a grown tree back to the forest floor, these hummocks are often used as a sign of forest maturity.

Logs are good for having fun, too. Children use them as balance beams. Small ones can be used to create forts. Hollow ones can be crawled through as tunnels, or lived in like treehouses. And I know one puppy who had a blast vaulting over them like agility jumps.



Woodpecker wuz here


While out hunting for fungus last week, I happened to notice quite a number of trees with woodpecker holes. The absence of foliage on the plants provides a much different view of the forest (or other habitat). Things that are usually obscured are now exposed. Sometimes it’s not that the thing was obscured, but rather that you just looked past it because there was so much going on that you were distracted by other things. But now with the leaves gone, and the ground cover under a thick layer of snow, other things start to pop out at you. Like birds’ nests (but that’s another post). It’s actually possible to determine who made the holes in the tree you’re looking at, if you know the characteristics to look for.

There are five species of woodpecker that regularly frequent the woods around my parents’ place. There are actually seven that can be found in southern Ontario, nine in Ontario as a whole, but only five that are particularly widespread. The first one is the Northern Flicker. These birds actually migrate south in the winter, and very few remain in the province during the cold months. This is because, although a woodpecker, their primary foraging method is by probing the ground for grubs. They will and do forage on trees, but you’re more likely to find them feeding on your lawn. Of course, when your lawn is under several inches of snow, it’s difficult for flickers to make a living. So they head south to warmer climes (this is unfortunate, because they are beautifully plumaged woodpeckers and would add a nice splash of colour to the winter landscape – do a google search for Northern Flicker to check them out).


The smallest of the remaining four is the Downy Woodpecker. They are the quintessential woodpecker of birdfeeders, the bold little guy who is often found hanging out at suet feeders (check out the suet feeder image in my previous post). My parents had some emergency roof repairs done last week, and at one point the workers were tidying up shingles from the ground by the house while the local Downy watched from the suet feeder six feet away. Being the smallest, they also make the smallest holes in trees. The holes in the above image are only about half an inch wide on the largest ones, and can be a quarter of an inch on the smaller ones. Because of their size, Downy Woodpeckers will often perch on goldenrod stalks with galls (those little balls you sometimes see halfway up the stem) and peck out the grub from inside. If you check out galls in the winter, as often as not there’ll be a hole in one side from a Downy (chickadees will also peck out gall larvae – you can tell who was there by the tidiness of the hole – chickadees are very messy as their bills aren’t as specifically designed for the job).


The Hairy Woodpecker looks superficially similar to the Downy, but is actually a larger bird, with a longer, stronger beak. Their handiwork can usually be found on dead tree snags or logs. Their typical hole is slightly larger than that of Downys, up to a couple inches, and often has a slightly rectangular shape to it. You’ll usually find a series of such holes in the log or dead branch, grouped together. The holes in the birch at the top of the post were probably also made by a Hairy. Most woodpeckers have barbed tips to their tongues that they use like spears to snag bugs or larvae hidden deep within the wood. These barbs are coated with a sticky saliva that makes them extra secure. A woodpecker’s tongue wraps back behind its skull, and can be as much as three times as long as the length of its beak! Check out the photos at the above link, pretty amazing.


The largest woodpecker in Canada is the Pileated Woodpecker (pronounced either pill-ee-ate-id or pie-lee-ate-id, depending on your preference – I say the former). These stunning birds are about the size of a crow, with a long neck with white stripes, and a gorgeous red crest. They’re such beautiful birds, I have to post a photo of this female I photographed foraging on my parents’ lawn a few years ago. You can tell she’s a female because, while both sexes have the red crest, the black “moustache” is actually red in males.


Lovely, isn’t she? While she’s foraging on the ground in this photo, Pileateds more often search for grubs on dead trees or logs, or even in live trees with heartrot (decaying inside, where you can’t see it – but the birds can tell!). With those massive, powerful beaks they can really do some damage. Pileated holes are often as big as, or larger than, your fist, going deep into the heart of the tree. As you can see in the photo above, the Pileated who hammered these holes dug into a live tree (the sap is dripping down the bark) into its decaying centre. It must have found a good haul, too, because it made many holes, and digging through the still-live outer bark is no easy feat!


Pileateds also have the power to pry up the bark off dead trees in order to get at bugs right underneath. In the photo above, the bird has removed most of the bark from the trunk by inserting its beak under a loose edge and using it like a lever to flake it off. On this particular tree the bird had started at about our eye level and worked its way all the way up to near the top, about ten or twelve feet of bark-flaking. Also another sign that there must have been good eats underneath!


Indeed, if we look closer, we can see the trails of bark beetles and their larvae. These trails went all the way around the trunk, and as far up as I could see. Speaking of things you see in the winter… but that’s also for another post. If you scroll back up to the Downy’s hole photo, you’ll notice that at the bottom there’s a small bit of bark flaked off there, too. It was taken on the same tree, and they were obviously interested in the same good food source.


The fourth, and final, woodpecker my parents get is the Yellow-bellied Sapsucker. And no, that’s not a made-up name! It is indeed yellow-bellied, and it really does suck sap. Or feeds on sap, anyway, if not by a sucking method. Sapsuckers lack the barbs that the other woodpeckers have, instead having a feathery texture that absorbs liquid to allow the bird to drink by lapping at the sap, much like a cat laps up a bowl of milk. Sapsuckers drill “sap wells” into live trees and feed on the sap that oozes out of the wounds. They have a characteristic habit of drilling in straight rows, like above, that are easy to identify. The sap produced by sapsucker wells is not only used by the sapsuckers themselves, but also provides food to other animals, such as some insects like ants and bees, and hummingbirds, who, particularly in the spring before many flowers are blooming, need an additional source of sweet food. Sapsuckers are also migratory, and leave for the winter. We haven’t seen the sapsucker pair that used to nest on my parents’ property for a couple years, and it may be they’ve died and nobody’s moved into their empty territory. The sapsucker holes in the photo are a few years old.


This last hole wasn’t made by any woodpecker! This is an example of a live tree with heartrot. In this case, a branch was torn off, likely in a storm, and exposed the decaying interior of the tree. Although the outside and branches look superficially healthy, it’s obvious the tree is in decline. Some of the sawdust from the cavity was on the ground at the base of the tree, and I suspect this hole is likely used as a frequent snoozing spot by a raccoon. Seems pretty cozy to me!