Exploring the Passenger Pigeon in 'A Feathered River Across the Sky' [EXCLUSIVE INTERVIEW]

The passenger pigeon was a magnificent species, spanning thousands of miles across the United States and Canada. Several accounts talk of their enormous flocks, darkening the skies for hours at a time as billions of them passed overhead and eclipsed the Sun. But unfortunately for this abundant bird, habitat loss and hunting by humans drove them to extinction in just a matter of a few decades. The last known living passenger pigeon, Martha, died 100 years ago at the Cincinnati Zoo & Botanical Garden, devastating conservationists everywhere. Given the extraordinary tale of the species, there has been talk of bringing it back through a process known as de-extinction, despite some ethical concerns.

In his new book "A Feathered River Across the Sky," author Joel Greenberg, a species expert and research associate at Chicago's Field Museum, goes into further detail about the passenger pigeon, not only delving into its biology and historical range, but also creating a cautionary tale and emotional story of its downfall. Greenberg recently took the time to speak with Nature World News about what first captivated him about the passenger pigeon, the circumstances that caused them to become extinct, and what we can hope to learn from them for the future.

[Editor's note: This interview has been edited and condensed.]

Q: What first inspired you to focus on the passenger pigeon?

A: When you read about birds of North America, the passenger pigeon looms up as a story unlike any other. The huge numbers, the concentrations, all attest to the incredible richness that was the forests of the eastern United States and Canada.

Having gotten interested in it, in my view there are three things about the pigeon story that are unlike any other. One is the sheer abundance of the birds. There were not scientific surveys done, but there certainly were billions and they were certainly the most abundant bird on this continent, and probably the world. Second, that abundance often aggregated in concentrations that are almost unfathomable today. The classic John Audubon account of a trip he took from Henderson, Kentucky to Louisville in the course of three days [says that] the birds literally eclipsed the Sun for the entire three days. And it's not just one guy [saying this]. People wrote about the birds darkening the skies for hours at a time going back to the 1600s. So I don't think there's any doubt that that's true.

Then the third element is that the depletion of such abundance in such a short time - at least as it applies to vertebrates - makes it unique. So I think those three elements really make this story incredible. Then you throw into it the people. There are just a variety of people who are involved one way or another and I think it just adds for a really compelling story that has lots of lessons relevant for today.

Q: You cite in your book that the spread of the railroad and telegraph lines in particular led to mass killings of these birds, especially because they did congregate in such large numbers. Do you think today's technology also poses a threat to existing species, birds or otherwise?

A: Absolutely. What I think might be the closest contemporary analogue to what happened to North American wildlife in the 19^th century is pelagic fishing. With technology like sonar, you can identify where the schools of tuna and shark are. It's not like the old age when you go out and see what you can find - you know exactly where they are. And then you have these factory ships that can remove all life that's bigger than the fishes in their net. There's a case yet where technology is making it easy to deplete the oceans. The other thing exacerbating that is also what happened in the 19^th century, where there's no sovereign to control it. So the federal government did not exert jurisdiction over migratory birds in the United States until the Lacey Act. It was introduced in the 1900s when the birds were already gone.

New technology allows us to learn so much more about these things, [so] hopefully this knowledge will let us proceed in wiser ways than we generally have in the past.

Q: Aside from human activity and technology, climate change is another threat animals are dealing with. What do you think the future holds for species of this era?

A: David Blockstein, a colleague, identified the four horsemen of extinction. There's direct take, and that's what we're talking about with the pigeons and the fish. B, there's habitat loss, that's fairly obvious. And third is invasive or introduced species. [For example], feral cats, according to the Smithsonian, kill a billion birds in the United States a year, and that's a problem. And fourth is pollution, which I tend to lump with climate change. Pollution at one level can simply render an aquatic environment unsuitable for life - it can change climate over time as your question suggests.

I think there are things that can be done... there are successes and places that are doing better. It shows that if we make an effort we can do good things.

Q: What do you think we've learned from the extinction of the passenger pigeon, if anything?

A: Well, it helped spawn the country's first great environmental movement. Out of that movement came the first bird laws, and we don't just slaughter birds in this country like we did then. We allow recreational hunting, but it generally is under a scientific regimen so that only so many can be taken and it doesn't jeopardize the survival of the species. That's a change. And the pigeon isn't the only reason, but it was certainly an important reason. People remembered the pigeon and it motivated them in part to enact those laws.

The other broad message that I like to point out has two sides to it: that just because something is abundant - it could be oil, water, or something alive - if we aren't careful we can lose it. There are seven billion of us on the planet - there are more of us now than there ever were passenger pigeons - so we need to be circumspect as we proceed. And the opposite side of that is if something as common as the pigeon can disappear in four decades, it shows that rare things can be gone in the blink of an eye.

Q: Some scientists are currently exploring the idea of de-extinction for the passenger pigeon. Do you think that's a good idea necessarily? Can you foresee any ethical or biological problems with that?

A: It inspires a lot of people. Some people think it's great, while others are a little fearful. They're not talking at this point about bringing back passenger pigeons; they're going to bring something back that has passenger pigeon traits. One article said it would take 20 years to create the first bird. If they were going to create flocks of it, it would take much longer. They're certainly not going to create hundreds of millions of birds. Whether they can actually bring back the passenger pigeon, though, I think is another question.

Q: It's been 100 years since the extinction of the passenger pigeon. What is one thing you hope readers take away from this book or learn about the species?

A: One, which I mentioned, is our use of resources and living things because if we're not careful, we can lose it. Second, is that things can be done. If you care about nature and if you think having a beautiful vibrant world around you is a good thing, there's lots of ways you can help make that happen.