The American crow is a common sight in Maine, and it used to be considered a different species than the smaller crows found in the Pacific Northwest. That changed in 2020. Credit: Courtesy of Bob Duchesne

I have a goal to see 700 bird species in North America. Getting there just got a little harder.

It doesn’t matter too much to most people. Most people appreciate the birds they see without making a big deal out of it. Those people are normal. Only a relative handful of us are abnormally bonkers. We keep lists. And topmost among those lists is the “life list” — a list of all the bird species we have seen in our lifetimes.

That’s where things get complicated. Keeping a world list is easy, because all birds in the world are eligible for listing. But most listers keep multiple lists, defined by geographic areas. For instance, I keep a North American list and a Maine list. You’d think a Maine bird list would be uncomplicated, right? But what if I’m standing on the pier in Eastport, and I see a rare gull across the channel? Can I count it if it is in Canadian waters? No.

Don’t blame me. I don’t make the rules. The American Birding Association does. The association exists to support recreational birders. Among its many tasks is to define consistent regions for listing, so that birders can compare their lists with others and know with certainty what birds are eligible for them to list. That can get weird. The group defines the “North American” area as all of the continent above Mexico, including the tiny French islands of St. Pierre and Miquelon, which lie just off the southern tip of Newfoundland. It does not include the Bahamas, Bermuda or Greenland.

If you think that’s complicated, here’s another question: What’s a species? The American Ornithological Society makes that determination. It also names the birds. The society exists to support professional birders — the scientists and technicians who do the research. It has published an official bird list since 1886. Periodically, the society entertains proposals for re-categorizing and renaming species based on the latest research.

That’s the cause of my woe. The 2020 supplement just came out, and I lost one species. Until now, there was a crow in the Pacific Northwest that was slightly smaller than the American crow; it had a more nasal voice. It was first declared a species when settlers arrived in the 19th century. I saw my first northwestern crow in Washington state about 30 years ago. It was noticeably smaller. Size matters.

But apparently, size doesn’t matter much to crows. Wherever their ranges overlap, American and northwestern crows interbreed with reckless abandon. Genetic research suggests that a small population of American crows was cut off from the other crows by Ice Age glaciers nearly half a million years ago. Over the next 400,000 years, northwestern crows evolved characteristics distinct from American crows.

Then the ice melted. As soon as the two species regained contact with each other, they romanced and canoodled their way back into each other’s hearts. As a result of rampant baby-making, their genetic differences melted away with the glaciers. In June 2020, the ornithological society announced that the northwestern crow no longer existed — that it was just a smaller version of the American crow. To birders on the West Coast, this was a relief. The species were intermixing from northern California through British Columbia, and nobody was too sure what they were seeing. It was such an aggravation that birders were actually sleepless in Seattle.

But to me, it was a deduction from my Life List. I lost one. I’m down to 601. At this rate, if I am going to see 700 species, I may have to live a little longer than planned.

However, it also works the other way. The diminutive northern saw-whet owl is a widespread Maine breeder. Its range extends through northern regions clear across the continent. All are genetically similar, with one exception. On a remote island group off the northwest coast of British Columbia called Haida Gwaii, there is a small population of owls that became geographically cut off from the continent. Over time, this race has become much darker and buffier. It has evolved different dining habits. The odds are good that someday soon, it will be deemed a separate species. I could add it to my life list. Admittedly, that’s unlikely. Nowadays, I can barely find the bathroom light switch in the dark, let alone find a tiny owl on an island 30 miles off the coast of Canada.

But if I did, that would be something to crow about.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.