I am keeping my eyes on the canopy, where spring and green leaves are still absent, but other presences are putting in an appearance.

Even with the seemingly unrelenting repetition of snow and melt and rain and slush, evoking descriptions of the landscape as “bleak” and “monotonous,” a certain amount of activity from animals still dominates the treetops — as still as they appear to be from a distance. On days when I am unable to get enough time outdoors to feel refueled by the natural world, I find myself scanning the near horizon for signs of life, and surprises.

The usual reward for this meager investment of attention comes in the form of raptors, the sentinels of the wetlands near tidal marshes, the obscured territories of forest margins interrupted by roads. Driving in early daylight along a certain stretch of Route 295 from Falmouth to Portland and back again at day’s end, I discover a whole population of birds and mammals busy about the business of survival.

One common predator along the roadway is the northern harrier, known too as the “gray ghost” or marsh hawk, the male a pewter gray in its plumage, perched absolutely still in the uppermost branches of leaf-ripped trees. I see it again and again, in roughly the same place, at the edge of the marsh, on a narrow cusp of land in which mice multiply, then die — prodigious reproducers who keep the raptors alive in the cold, mostly colorless, world of the treetops.

Even in the few seconds it takes for an internal combustion machine to hurtle past a piece of woodland not yet felled, I am able, every now and then, to glimpse particularly splendid raptors: a red-tailed hawk, a merlin, a peregrine falcon. Perhaps a dozen times I have watched a bard owl, still as stone, oversee the rim of the bay.

But mostly they confine their cameos to the woods around the cabin, coming in low over the rickety deck that now is a platform of hardened snow, trawling in air for a sign in the frozen white froth below for a skittering mouse or unsuspecting cottontail.

Last week, though, I saw something I had never witnessed before: a porcupine, plumped up, high in a tree by the highway, gnawing on bark. From a distance, my mind — prepared to see only something predictable and slightly odd, but within reason — had run through a range of options: a plastic bag blown into the branches; a giant-sized gall of some sort, a whole larval world waiting for spring; some anomaly of development — the most mammoth pine cone imaginable.

The last, particularly, would have been impossible but the gears of mental inventory turn first, always, to the familiar, and failing that, open to the unexpected, and to delight — exactly what I found.

There it sat, a porcupine rolled into itself, grasping a branch and pressing its hind end against the trunk for better balance and more secure purchase. With the sun behind it, all the quills of its rolled back were silhouetted like so many needles of dark piercing what was left of daylight.

My senses were spinning, trying to recalculate the location of a creature that was always a ground-dweller in the imprecise catalog and classification of species in my mind. My musings over porcupines tend to focus on old myths of the rodent’s ability to “throw” its quills at predators — a fanciful notion no doubt borne of the pain of a dust-up with the all-too-effective defense mechanism the animal possesses. Quills barbed like hooks, a delicate extraction.

But it turns out that the porcupine is a prodigious if slow and lumbering climber, and depends on the bark, phloem and cambium of trees, especially conifers, for much of its winter diet. It so commonly is engaged in this gorging that it is considered a pest. It can almost denude a tree of bark, often working a ring around a branch or girdling the trunk, and in doing so, killing the tree.

In spring and summer, porcupines return to earth to forage, feeding mostly on grasses, sedges, acorns and flowers. They are known to intrude on food crops and have even been seen gnawing on a Michelin or two.

But I was momentarily stunned by the sight, as odd I thought “as seeing a snapping turtle in a sapling,” as I told a friend later that night. It seemed it just should not be there, but it was, and by turning up, unexpected, it impressed upon me once again the marvelous surprises nature delivers without thought or provocation.

For a moment, our worlds collided — the porcupine’s and mine — and the impact blew a hole in my brain, stopping all thought other than awe. We know now what it means to have heavy reality hit from out there: the asteroid drove that home, and then some.

But there are all kinds of alien objects, and subjects, descending on us like cosmic castoffs. This morning several crows are dropping out of the treetops like sheets of ash, onto the snow, where last night I tossed scraps of raisin bread like broken stars in the dark.

Over the weekend, the first flying insect of the season — a sluggish mayfly — trembled in uneven arcs around my head as I returned home from the grocer’s. The owls are evident almost every evening, silent as death, here and gone and back again before you know it.

All the borders of the world are crumbling, as the season comes apart at the seams and spring seeps into the air. Porcupines in trees. They’ve always been there, I know now. But for a moment, they snapped my self-oriented thoughts like worn piano wire, snapped them sure, and put me where I belong, in harmony with nature and back in tune.

North Cairn can be contacted at 791-6325 or at:

ncairn@pressherald.com