Counting Species on a Little Patch of Earth

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.

In fact, probably what is the oddest about the living things on our property is the inordinate amount of attention, bordering on the bizarre, that we have paid them. This obsession stems, in large part, from a decision I made one winter solstice.

On that darkest, deadest day of the year, I decided to try to document and tally every species at our house. I was supposed to be finishing a long-overdue book, a process that makes every other potential project seem fascinating and urgent. I knew there was (and, in fact, still is) no spot on earth for which a complete species inventory has been accomplished, even with the help of millions of dollars and teams of international experts. In other words, the task was beyond impossible. But I had a book to finish, so I started anyway.

A species tally is an entirely different lens through which to see your daily life, and it leads immediately to one burning question: Which species should count? Does a bird spotted in the neighbor's yard count? What about the species of fir tree that was used to make the window trim? Can you count a species if it leaves behind nothing but scat or bite marks?

I set ground rules in an effort to capture the essence of what made up the life within our lives. Any species made the list, whether it showed up as a whole organism or just a part, whether it was in the yard or house or nearby, as long as it could be seen or heard or smelled or its presence could otherwise be detected from our property.

The vast and ever-changing diversity of our home quickly came into focus as Merrill and I and our two children began reeling off what we'd seen. There were Homo sapiens for sure, the raccoons that got into the crawl space, the meal moths that haunted the pantry, the hummingbird that flew in the window, the enormous spiders that prowl the basement laundry room every winter, and of course the range of creatures that have been our companions over the years, including dog, tortoise, rubber boa, garter snakes, gecko, scorpion and beetles.

I peered into the refrigerator. There sat parts of species of every sort and variety — more than I could begin to count in the condiments alone! I was floored by that infinitude of life and by the fact that it changed each week as we unloaded groceries.

Our unimpressive lawn became a kaleidoscope of mysteries, just one square foot of it boasting multiple species of grasses, one species of dandelion, countless other unknown plants that quickly came and went, and no end of insects, algae, mosses, worms, bacteria and fungi.

Every beam of slanting light, every breath of wind, every flitter of movement revealed something unseen. A droplet of rain splashed on the deck, a potential marvel of aquatic life. A newly noticed stain on the fence proved to be a burgeoning lichen. A squirrel ran into the yard and paused to scratch itself, prompting Merrill to yell out: "Squirrel fleas! New yard species!"

And it was clear that many more species were going by— in the night sky, in a robin's intestine, hiding under a leaf, silently creeping past — that we were missing entirely.

In hopes of seeing more, I installed a device known as a dripper, which creates the plink-plink sound of fresh water that is supposedly irresistible to many bird species that would never deign to visit a seed or suet feeder. Sure enough, as the spring migration moved through, gorgeous jewel-colored species known as warblers, of a sort we'd never seen in our yard, dropped right out of the sky to drink, bathe and frolic.

Amazed by these visits, we began to fantasize about what else we could bring in by displaying other enticing items — cut fruit, fresh steaks, rotting fish, a chattery bird, a live mouse. Out of respect for our neighbors, not to mention the feelings of the chattery bird and the mouse, we opted against hanging anything but laundry on the laundry line. Still, we wondered what we might be missing. A peregrine falcon? A snowy owl? The cougar that hadn't been seen on the street since it stalked the newspaper carrier several years ago?

One night, Merrill hung up a black light, which uses the same bulb that gives that magical purple glow to black velvet posters. It also attracts insects, and by morning a whole new world of nocturnal life was revealed to us. The attached trap held many more species of moth than we had seen before. There was even a water boatman, an insect named for the canoelike body with which it paddles about in streams or ponds — even though there was neither stream nor pond near us.

I wish I could give you a bottom-line species count, but I can't. Living organisms are reliably, inspiringly unpredictable, as any birdwatcher can attest; in years of watching, we have seen many species only once, so it is very likely we have missed many more. And though we are good at spotting birds and insects, we are nearly plant-blind, so who can say what botanical change has been afoot here? The same is true for the many, many microscopic things we literally cannot see.

And that moth that I was the first to see alive in North America? Actually, I'm virtually certain I wasn't the first. It was the first live Oecophora to be identified on this continent, perhaps, but others had been found dead in traps and live ones were spotted elsewhere soon after. In fact, earlier on the very day that Merrill caught the moth at our house, my daughter's friend pointed out a colorful moth that might well have been Oecophora. For those, like children, with eyes open wide, rarities can abound.

On any given day, of course, you're not likely to spot an unexpected guest. But one day it will happen. While you slice a grapefruit or fold laundry or sit at the computer, something unbelievable will be creeping or flittering through your life. Look for it, just in case.