Bring Back the Passenger Pigeon

A little over a century ago, the last passenger pigeon on Earth fell off her perch. An elderly female called Martha, she was the last of a species that used to flock in the billions. The collective beating of their cobalt-blue wings was like the rumble of thunder, and the draught it created was enough to chill those standing on the ground below. Once the most abundant bird in North America, there were, at one time, more passenger pigeons alive than people. A single flock could stretch over 100 miles long and take days to pass overhead. An avian eclipse, they blotted out the sun.

Beaky blinder!
Stuffed passenger pigeon at the Harvard Museum
of Natural History. Credit Laura Poppick. 

And then, one day, they were gone. In the nineteenth century, they were shot, clubbed and blasted form the skies by men who sold them for their meat. The cheapest source of protein in the United States, passenger pigeons became big business and most ended up baked, stewed or wearing pie-crust lids. Their numbers plummeted perilously but by the time anyone noticed and protective legislation was introduced, it was too late. There were no passenger pigeons left to save. The last of a species that had thrived for millennia, Martha spent her final days caged in the Cincinnati Zoological Gardens, Ohio. Aged and immobile, visitors pelted her with sand to make her move, so in the end her keepers had to cordon off her enclosure. And then, on 1 September 1914, Martha died. The passenger pigeon was no more. It ceased to be. It expired and went to meet its maker. What a sad, sad story.

But plans are afoot to bring this iconic species back to life. Under the banner of the ‘The Great Passenger Pigeon Comeback,’ scientists from the non-profit organisation Revive and Restore are working hard to de-extinct the ‘Blue Meteor’ (as it was also called). It’s an extraordinary project that is already well under way. It involves a blend of cutting edge genetics, cell biology and some good old-fashioned pigeon breeding. Over the last couple of years, I’ve had the privilege to chat with the project’s lead scientist, Ben Novak. We’ve talked in detail about how the feat will be achieved. I discuss this in depth in my book, ‘Bring Back the King: The New Science of De-extinction,’ so I won’t go into it here. But in our most recent catch up, we debated an equally pressing issue.  Just because we can de-extinct something, doesn’t automatically mean that that we should. So why is bringing back the passenger pigeon a good idea?

Why do it?

Novak has spent the last few years pouring over historical records of the bird, and genetic data prised from the many preserved specimens that lie in museums around the world. It forms the basis of his Master’s thesis. Bringing back the passenger pigeon, he concludes, isn’t an act of academic curiosity; it’s an act that will shape the deciduous forests of the eastern US in a profoundly positive way. It will benefit, not just the trees, but the animals and other plants that live in and around them. It will boost biodiversity and help to regenerate woodlands.

These are bold claims for a species best remembered for the devastation it wrought. Records reveal how, when a flock came to rest, the birds would pile on top of one another, breaking boughs and bending branches. Whole trees were toppled. Nomadic by nature, the birds would land in a mast-laden forest, devour every morsel they could find, cover the ground in guano and then take to the skies in search of another roost to ravage.

But in the aftermath of this avian apocalypse came life. The closed canopy woodland became open again, explains Novak. Sunlight was able to reach the forest floor, where the guano fertilised the earth and new plants and flowers grew. In turn, this attracted a whole host of birds, amphibians, insects and mammals. The whole landscape changed. It became more biodiverse, more vibrant, more ‘alive’ … until the closed canopy regrew and the cycle started again.

“These were ecosystem engineers,” he says. But because they were nomadic, and moved around a lot, the regeneration wasn’t uniform across the landscape. It was patchy. So different parts of the forest were in different stages of the regeneration cycle at any one time.  Bring back the passenger pigeon and these natural cycles of regeneration will resume, he argues.

But ecosystems don’t stand still. When species go extinct, landscapes change in profound ways. Think, for example, of the woolly mammoth. When it disappeared, the lush, fertile grasslands of its heyday were replaced with barren, scraggy tundra. Critics of the Great Passenger Pigeon Comeback argue that it’s former habitat has changed too much, that the landscape is ‘too far gone’ to support a 21^st century version of this beloved bird.

Novak, however, has evidence to suggest that passenger pigeons have been disturbing the forests of the eastern US for tens of thousands of years, and that during that time, they persisted in perpetually large numbers. Forests came and forests went. There were times when conifers proliferated, periods when deciduous trees gained the upper hand, but it mattered little. With their generalist diet and their wing-fuelled wanderlust, the passenger pigeon kept on moving on, sculpting the ecosystem along the way.

“It doesn’t matter that the forest is different today,” says Novak. “The only forest they need is one with trees in it. Bring it back and it will restore vital ecological functions to the eastern US forests.” 

Sounds like a pretty good argument to me.