This window does not face onto pristine wilderness. It looks at my neighbor’s bathroom window. My street in this small former mill town is crowded enough that when someone sneezes in a backyard, the person next door is likely to say “gesundheit.”

Yet out of that window — actually on the window — I saw a creature that I would later learn had never before been seen alive anywhere in North America. It was a tiny moth less than half an inch long, with elegant forewings held tentlike over its back, each painted in fluorescent yellow, iridescent blue, and black. All I knew was that my husband, Merrill Peterson, who is an entomologist at Western Washington University, ought to go out and catch it with his net, which he did.

After several weeks of reading and e-mailing scientists near and far, some of whom would become his co-authors on a publication about the moth, Merrill learned it was Oecophora bractella, a denizen of Europe’s woodlands and a species rare throughout most of its range, even considered threatened in some areas.

It was the sort of sighting we knew would never happen at our house again. Until Merrill came across another species in the backyard — one that had never been seen on the West Coast — a relative of wasps and bees known as a sawfly. And the list of unexpected species that have shown up, sometimes actually on our doorstep, has only grown longer.

It was enough to prompt us to ask if there was something really special about our home, something ecologically unique. But if I invited you over for a look at our unassuming little yard, I think you would come to the same conclusion that we did. There simply is not.

It’s true that our part of northwestern Washington, also known as the Fourth Corner, is the entry point for goods, people and vehicles coming from points north and west. We are quite likely to reap more than our share of the whirlwind of introduced species that humanity has been rapidly sowing around the globe. But most of the unexpected species on our list have not come as part of some wave of foreign invasion.

So what exactly is going on? The very same thing, I’d guess, that is going on at your house and everyone else’s. Any patch of earth, large or small, turns out to be a mad surprise party of species — fluid, unpredictable and wild — and a microcosm of what is happening and has always been happening around the corner and around the globe.