December bricolage

a familiar woodpecker, eagle art, and an assortment of snow-loving bugs

A female hairy woodpecker visits my suet feeder regularly, and I’d bet any money that she is the same one that came all summer long, as a juvenile, in the company of a male, presumably her father. She learned well from her dad, and she still comes.

One day in mid-December, I spotted her wrapped around the suet feeder, her tail curved around one end as she pecked away at the other end. A sudden fluttering caught my interest, as another woodpecker landed briefly, to snatch a quick bite. The new arrival stayed just long enough that I could see her small bill and also see that she was much smaller than the hairy woodpecker. So there was no doubt about it; it was a downy woodpecker. I’m told that they seldom nest in our area but we sometimes see them in the off-season.

On a gray and foggy day, I turned on to the road by the Pioneers’ Home, where the line of young cottonwood trees is often used for perches by eagles scrounging from the nearby dump. On this day, half a dozen eagles were hanging out on the cottonwood branches. In the fog, the eagles were black, the graceful branches were black, the whole array artistically displayed like silhouettes on a silvery backdrop. Splendid!

A few days later, I wandered down the east shore of Mendenhall Lake, then cutting over to the Moraine Ecology Trail. Some post-holing, some bush-whacking, a wet foot from finding a soft spot in the ice—but the quietness was pleasing. The sound of Nugget Falls and scattered raindrops tapping on my cap—that was it. Aaah—maybe a red squirrel chattering over in the woods. I found a thriving, bright green patch of stiff clubmoss, poking perkily up out of the snow, still bearing immature cones. Surprisingly, there were no hare tracks, but beavers had been busy in a couple of places, packing down a trail between ponds, dragging a few branches over the snow, and starting new cuts on some big cottonwoods. An ermine had bounded from one clump of brush to another. The only observable activity was provided by two small, flying insects, maybe midges.

Seeing those little fliers reminded me of other ‘bugs’ that come out on the snow, at least on days of mild weather (although some caddisflies spend the whole winter as winged adults). Several kinds of arthropods, from many different taxonomic groups, can be active in winter; here are some of them: a variety of tiny flies known as midges are active in winter; most fly about but others are flightless.  Males of a moth called Bruce’s spanworm fly in late fall and early winter, mating with wingless females that lay their overwintering eggs in protected sites such as bark crevices. There are winter-active craneflies that dance in swarms, mostly in fall and spring but also in winter, and stoneflies that emerge in late winter, crawling onto land to mate. A fungus gnat can tolerate very low temperatures because it has an antifreeze protein in head and thorax (but not the abdomen, which can freeze and apparently thus reduce evaporative water loss). The famous iceworm (it’s really a worm, somewhat related to earthworms) lives on glaciers, crawling down into cracks and crevices where the temperatures are said to stay about thirty-two degrees Fahrenheit; so they don’t freeze and can go on feeding on microscopic algae and detritus.

Springtail. Photo by Bob Armstrong

And then there are the springtails, non-insect arthropods, most of which can hop about using a forked appendage on the abdomen. Several kinds can be found hopping or crawling over the snow, looking for microscopic bits of food or dispersing to new places. Their predators are out too, including spiders, beetle larvae and danceflies (see photos). A study of one kind of dancefly found that males swarmed near selected landmarks on sunny, windless days in winter, at temperatures as low as eight degrees centigrade. The males carried captured insects to lure females to the swarm, presumably eventually using the prey as a courtship gift.

A dance fly with a springtail. Photo by Bob Armstrong

Thanks to Bob Armstrong and John Hudson for guidance about winter arthropods.

January jaunts

midwinter insects brighten a cold shady hike

After a series of gray, drippy days in early January, there dawned a glorious blue-sky day. A group of hikers took advantage of it to wander up to Cropley Lake above the Eaglecrest lodge. The sun was still too low in the heavens to peek over the ridges, so we sat in the shadows to down our lunches. Most of us did so, anyhow; two of the gang peeled off to find some sun, somewhere, to warm their lunch-time.

Those of us who roosted on the shores of Cropley Lake may have lunched in the shade, but we had a fine view of several skiers swooping elegantly down from the top of Ben Stewart. Not content with climbing up Ben Stewart and having a fine ride down, the skiers then zig-zagged up a broad talus slope to the next ridgetop, to find another sweet trip down. We, being ‘of a certain age’, could only watch with stifled envy and much pleasure.

Wildlife was notably scarce on most of our little explorations, and we had to settle for very small types. We found tiny (about four millimeters long) flies that experts identified as a kind of dance fly. Unlike some kinds of dance flies, these were not forming mating swarms of ‘dancing’ flies but were all scattered around on the snow or just above it. We found one pair in the act of mating. This kind of dance fly is predatory. The larvae live in fast, cold, clean running water, hunting over and under the stones for midge and blackfly larvae. The adults prey mostly on other flies. The adults we saw could not be finding many flies at this season, so perhaps their main goal is finding mates.

Dance fly. Photo by Bob Armstrong

Near the glacier, we also found a few adult caddisflies on the snow. These might be the ones called ‘snow sedges’. Clearly, they are not the plants known as sedges, so I was curious about the name. I’m told that ‘sedge flies’ may be a name used by the British for certain kinds of caddisflies (perhaps because they are sometimes found on sedge plants), and artificial flies that mimic caddisflies are called ‘sedges’ by fly-fishers.

The caddisflies sometimes known as sedge flies have aquatic larvae that live in nifty little cases built of leaf fragments, conifer needles, or tiny pebbles. They typically forage by shredding decaying vegetation, especially leaves that have been partially decomposed by fungi. The fungi on the decaying leaves are part of the diet too, and sedge flies are fussy about the kinds of fungi they eat. Some sedge flies, including one of our local species, also graze on salmon carcasses, and many of them also collect miniscule bits of floating debris created by the shredders.

The small flies and the snow sedges are among the few adult insects that are active in winter. There are also stoneflies that leave the aquatic larval stage and fly around looking for mates in winter (see Empire 31 March, 2011). Why do these few insects emerge as flying adults in winter, when temperatures are low and snow covers most of the ground? One advantage might be that there are fewer predators, such as songbirds, spiders (although some of these roam over the snow in winter), or wasps. But what is the cost of emerging in winter?