The phoebe returned with his repetitive racket in mid-April. A few days later the juncos blew through. Or, really, they were here just that one day, so maybe they rolled on because at the time 2 feet of gravel-addled snow still surrounded the driveway.

And, as always, we have seen and not seen the robins.

Seen because: Sometime around then a robin was poking around out by the shed. Not seen because: Or was it several robins? Or was that last year? As if the phoebes and juncos were family members, while the robins barely existed.

Of course, the robins have always been there. Because of their brick-red fronts, they were the easiest bird I learned to spot when I was a boy just upwind of Portland. More robin images have probably formed on my retinas than any other species of bird except possibly crows and gulls and chickadees. But because they’re so familiar, I hardly even see them.

Case in point: In January I was amazed to come upon what appeared to be hundreds of robins squawking, chattering and bouncing around the branches of bare hawthorn trees beside a parking lot. “What’s this?” I thought. “A whole biosphere of robins in the middle of winter?” I’ve never seen this before.

Or check that — never noticed it. As it turns out, it’s not an unheard-of phenomenon. Turdus migratorius, true to its species name, is migratory, and its range is enormous, stretching over most of North America from breeding grounds in Labrador and around Hudson Bay down to winter digs in southern Mexico. The year-round territory extends from Canada and Maine to Southern California and Florida. They start making their way north as early as February. So robins in winter are not anomalies.

I just never noticed. You can tell from this that I’m not an excursionary bird-watcher. I mostly keep track of my own little backyard avian cosmos. Chickadees, nuthatches, phoebes, juncos in spring and fall, hummingbirds buzzing us in summer, blue jays by the task force, woodpeckers and flickers, sparrows, mourning doves, passer-by warblers, wild turkeys, the occasional owl or hawk reconnoitering for voles, once in a while a goldfinch, vireo, pheasant. Canada geese clattering along designated air traffic patterns above the treetops. Once there appeared to be an ovenbird meditating silently in the brush off the back door. Crows, of course, and sometimes a thrush.

When I say thrush, I’m picturing a wood thrush. But what I really mean, practically without knowing it, is robins. Come to think of them, they’re there a lot, pulling worms out of wet earth, hopping around under the red osier dogwood, holding their chests out and their heads up on perpetual red alert. In spring they’re after early bugs, but their diet, according to the guidebooks, is a mix of animal and plant, depending on what’s available.

The males get here first in spring and mark out nesting territory by song. They prefer maples and spruces, it seems, and sometimes last year’s nest is revamped by the female. Like most birds, they practice well-honed domestic routines. The female sits on the clutch of blue eggs, and the male guards the homestead.

Not surprisingly, there are definite communication networks invisible to us, but essential to the robins.

They defend their territories by mobbing — cooperatively harassing, buzzing, shouting at, and even attacking a threat to the nest — and they apparently talk about strategies. Researchers have parsed from robin-speak two calls used during predator threats, “chirps” and “chucks.” Robins that attacked a blue jay chirped, while others that held back and did not actually attack chucked. They used the same warnings for snakes, but at a lower frequency of vocalization. The researchers believed the robins were communicating not just warnings, but defense strategies (to attack or not attack).

After the chicks leave the nest, they stay home for a while, and the male continues to take care of them until their foraging skills are fully functional. Domestic responsibilities like this are characteristic of most birds, not to mention other creatures as diverse as cats, wolf spiders (who ride around safely on their mothers’ backs after they’re born), and humans. The care and feeding of young certainly looks a lot like some kind of a force we all practice together. Even though it’s so familiar, you don’t really see it unless you look for it.

All this about the robins is new information to me because I just haven’t paid much attention to what I’ve already seen in abundance. And make no mistake — even though you might not notice them, robins are one of the species that have profited from human development and by all accounts are thriving.

So many robins, and so little awareness on my part. It makes you wonder what else is right before your eyes that you’re not seeing. Like fish debating whether there’s such a thing as an “ocean.”

Dana Wilde lives in Troy. His writings on the curiosities of his backyard are collected in “The Other End of the Driveway,” and he is a contributor to “Pluto: New Horizons for a Lost Horizon” now available from North Atlantic Books. You can contact him at naturalist1@dwildepress.net. Backyard Naturalist appears the second and fourth Thursdays each month.