Extinct means “no longer existing.” Gone. Not Coming Back.

Extirpate means “to destroy completely.”

We humans extirpate too many of God’s beautiful creatures to extinction. This has dominated my thoughts after recently reading “Moonbird” by Phillip Hoose.

If he’d been in the Olympics, no one would have touched him in the marathon. In his 20 years of life, Moonbird, a rufa red knot, has flown more than 325,000 miles — a distance that could have taken him to the moon and halfway back.

In his astonishing 9,000-mile annual migration between the southern tip of South America and the Arctic, Moonbird sometimes flies 5,000 miles in six days without stopping. I get exhausted flying from Maine to Texas, a distance of 2,000 miles — and I’m just sitting in the plane.

Hoose, a Maine resident who has worked for The Nature Conservancy since 1977, says Moonbird, labeled B95 for his leg band identification, “has to be among the toughest four ounces of life in the world.”

He’s got that right. This bird’s inspiring story, however, is tempered by the fact that in B95’s lifetime, the worldwide red knot population has collapsed by nearly 80 percent. A key problem has been the over-harvesting of horseshoe crabs in Delaware Bay, where red knots gorge on crab eggs to sustain their long migration north.

You can guess who is responsible for the over-harvesting. For a long time, we pulverized millions of the crabs, grinding them into fertilizer. Today, they are chopped into quarters and used as bait to catch conches, whose meat is prized for many dishes from salads to marinara sauce to Asian stir-fry.

The crabs also are used in scientific research. Now the horseshoe crab, a 350-million-year-old species, is on the brink of extinction, along with the red knots that depend on their eggs.

Hoose told Meredith Goad, staff writer for MaineToday Media, “I wanted to write about extinction, but focus on a creature that was in trouble but not in the pit.”

A friend suggested the red knot, saying, “It’s got everything. It’s the ultimate long-haul trucker. It migrates from the bottom of the Earth to the top. It’s beautiful, especially in its breeding plumage. It’s tanking. The numbers are going down year by year by year.”

And so, we have “Moonbird, A Year On The Wind With The Great Survivor B95,” published by Farrar Straus Giroux. I hope it’s flying off the shelves, because this is an amazing story — with an important lesson for all of us in the tragedy of extinction.

This is one tough bird species. Red knots pork up on proteins that they convert to fat for their flights and enlarge their hearts. Their leg muscles wither and their gizzard shrinks. Then they are ready for takeoff.

The photographs in the book are astonishing, and the writing is crisp. I also enjoyed the brief biographies of the key people working to rebuild rufa populations.

Consider young Mike Hudson, a Baltimore teenage birder, who learned about the problems of red knots on an Audubon bird walk. He made a school presentation that led to a letter-writing campaign to the U.S. Fish and Wildlife Service urging that the bird be listed as an endangered species (www.friendsoftheredknot.org).

I’m not a big fan of the federal endangered species act, a program dominated by lengthy, mind-boggling, contentious processes fueled by lawyers and lawsuits. Most of the money allocated to the program goes to these processes, rather than the endangered critters.

The red knots don’t have time for this.

Meanwhile, B95, Moonbird, flies on. Seen on May 28 in Delaware Bay on his way north, we can only hope he’s successfully raised another family with those strong Moonbird genes and is, this month, arriving in Mingan at the mouth of the St. Lawrence, en route south to another winter in Tierra del Fuego.

We can also hope that in the group of first-year knots that will fly the same route a few weeks later, is a bunch of baby Moonbirds tough enough to stave off extinction for these wonderful creatures.

Because they can’t depend on us. Despite our fascination with sustainability, the barrage of advertising trumpeting our “green” industries and businesses, our state and federal endangered species acts, and our love for all things wild, red knots are flying to extinction.

Are we are smart enough to stop with the extirpation, before Moonbird’s relatives go extinct? Who knows? Perhaps in saving red knots, we’ll save ourselves.

George Smith can be reached at 34 Blake Hill Road, Mount Vernon 04352, or georgesmithmaine @gmail.com.