Feeling birchy

In the winter, from a distance, trees all tend to blend together in the landscape. The exceptions of course are the evergreens, whose colour stands out against the grays of the rest of the winter forest, and the birches, whose white bark sets them apart. In our area, our forest is predominantly oak and maple, but there are patches of birch here and there. Most of them are Paper Birch, Betula papyrifera, also known as Silver Birch, White Birch or sometimes Canoe Birch. There are 13 species of birch in North America. Several of them have names reflecting the colour of their bark: White, Silver, Red, Gray, Black, Yellow.

It’s obvious to see where the name Paper Birch comes from. The bark peels and hangs in broad curls from the trunk of the tree. Virtually all birches have such papery bark, but of the species that occur here in the northeast, only the Paper Birch peels in such a way. The paper curls, compared to the bark of other trees, are extremely resistant to degradation and weathering because of a resinous oil contained within it. This same property also made it ideal for siding watercraft with, and the Native Americans used it often for their traditional birchbark canoes. It’s also used as a building material in many birds’ nests, including vireos; whether they choose it for its waterproofing properties or its pleasant perfume I don’t know…

The name Silver Birch is often used to refer to Betula papyrifera, but the name really belongs to a European species, B. pendula. This is funny, because I remember learning a Canadian folk song as a kid, sung in rounds over campfires, called “Land of the Silver Birch”:

Land of the silver birch, home of the beaver,
Where still the mighty moose wanders at will;
Blue lake and rocky shore,
I will return once more.
Boom-diddy-boom-boom, boom-diddy-boom-boom, Boom-diddy-boom-boom, bo-oo-oom

High on a rocky ledge I’ll build my wigwam,
Close by the water’s edge, silent and still;
Blue lake and rocky shore,
I will return once more.
Boom-diddy-boom-boom, boom-diddy-boom-boom, Boom-diddy-boom-boom, bo-oo-oom

My heart grows sick for thee here in the lowlands,
My heart cries out for thee, hills of the north;
Blue lake and rocky shore,
I will return once more.
Boom-diddy-boom-boom, boom-diddy-boom-boom, Boom-diddy-boom-boom, bo-oo-oom

Land of the silver birch, home of the beaver,
Where still the mighty moose wanders at will;
Blue lake and rocky shore,
I will return once more.
Boom-diddy-boom-boom, boom-diddy-boom-boom, Boom-diddy-boom-boom, bo-oo-oom

Also in our area are Yellow Birch, Betula alleghaniensis. Their bark shines in the sunlight, and I think they would be more appropriately called Golden Birch. They show the characteristic birch curls, but they’re little, and narrow. You certainly would have trouble siding a canoe with them. Yellow Birch usually grow in damp soils, usually along the sides of creeks or vernal pools. They’re often found in association with Eastern Hemlock, which also prefer the same sort of conditions. Because of their habitat preferences, they’re found more locally and are less abundant than Paper Birch, which favour drier upland forest. Interestingly, apparently the twigs of Yellow Birch will, when scraped, produce a mild scent of wintergreen because of the methyl salicylate oil the tree produces, but I didn’t know this at the time I was out looking at the trees; I will have to check next time I go back.

Birches tend to be pioneer species; that is, they are the first trees to move in to an area after significant disturbance such as fire or clearcutting. They are often found in stands of relatively even ages as a result, and will also die together as they reach the end of their lifespan. I have found a couple of spots in our forests where it seemed every single birch was dead or rotting, covered in bracket fungi. Paper Birch, and possibly Yellow Birch as well, provide an important food source to many animals that rely on the bark during lean winter months. Moose, in particular, feed heavily on birch bark in the winter, and White-tailed Deer, Snowshoe Hares and Porquepines will all nibble on the bark of trees of various ages. The green leaves are also eaten by deer, but not usually dried leaves. Birch are one of those trees that have marcescent leaves – they retain them through the winter – and one of the hypotheses for this is that it protects the young twigs from browsing by deer.

Birches are host to the caterpillars of many species of lepidoptera and the larvae of other insects. One such species is the above, The Infant, Archiearis infans. These moths are daytime fliers and emerge in the early spring, often while there are still patches of snow on the ground. They seek out open, sunny spaces, and are usually found within or near to birch stands – not surprising, given that birch is their host plant. In areas with lots of birch they can be quite plentiful, but even in forests with sparser birch numbers they are still common. While out today I encountered 8 along a 1 km (0.6 mile) stretch of road. It’s possible you may not realize that what you’re looking at is a moth when you see it – often they spring up from the road before you get a good look at them, and in flight they just look like a small, orange, flighty butterfly.

This second one also favours birches as its host plant. It’s the Scarce Infant, Leucobrephos brephoides, related to the first above. As the name implies, this species is significantly less common than The Infant, and despite feeding on a widespread and common tree species, and found across much of northern North America, the moth species itself tends to be localized and rare. I was lucky to discover one along our road, resting in the middle of the dirt surface. I initially mistook it for the orange variety, and it was just sheer luck that I happened to get my butterfly net over it (which I’d taken along with me this walk, since I wanted some photos and it’s tricky to sneak up on these guys).