There was a time when the passenger pigeon was the most abundant bird in North America, if not the world. With cobalt wings and a peachy breast, their flocks were once so vast, they took days to pass overhead. Like an avian eclipse, they blotted out the sun, and it’s said that the collective beating of their wings was so powerful that it chilled the ground beneath them. They numbered in the billions, and then, one day, they were gone.
Human greed was to blame. In the 19th century, passenger pigeons provided a seemingly inexhaustible supply of protein. They were netted, clubbed and shot from the sky. They were poisoned with whisky-drenched corn and asphyxiated with smoke and sulphur. By the time any meaningful legislation was introduced, there were very few passenger pigeons left to save. The last individual, a female called Martha, died at the Cincinnati Zoological Gardens on 1 September 1914.
How could the passenger pigeon be brought back from extinction?
Working with Revive and Restore, the scientist Ben Novak is now leading ‘The Great Passenger Pigeon Comeback.’
Remember that any de-extinction project needs a source of DNA and also a close living relative. There are many museum specimens from which to extract DNA, and there’s the genetically similar band-tailed pigeon, which is common and native to North America.
Cloning doesn’t work for birds, so the plan is to collect some very specific cells from embryonic band-tailed pigeons. The cells, called primordial germ cells, have the ability to make eggs and sperm. Scientists will edit them, so they contain passenger pigeon genes, and then return them back to the embryonic birds.
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When these band-tailed pigeons grow up, they will then produce passenger pigeon egg and sperm. Allow them to mate, and the unusual birds will produce a passenger pigeon. This means that the world’s first de-extinct passenger pigeon will have a different, albeit closely related species, for a mum and dad.
Should we bring passenger pigeons back?
Novak, who has researched the bird’s ecology, believes that passenger pigeons could play an important ecological role if they were to be released back into the deciduous forests of eastern North America.
Historically, when the vast flocks roosted, they trashed things. Saplings were toppled, branches were broken, and the forest floor was carpeted in guano. But from this apparent devastation, sprang life.
The droppings fertilised the soil and the sunlight kissed life into the grasses, flowers and shrubs that regrew. This provided habitat for insects, reptiles, birds and mammals. The land became productive and diverse, until the canopy closed over and the cycle started again. Passenger pigeons drove this cyclical rejuvenation of the forests, and in their absence, the closed canopy environment predominates. Bring back the passenger pigeon, the argument goes, and the cycle can restart, boosting both forest regeneration and biodiversity.
To achieve this ecological goal, there would need to be large numbers of passenger pigeons, but how ready is America, for birds that flock in the millions of millions? Make too few, and the birds will be ecologically impotent, but make the really big numbers required to sculpt forests, and they could become a nuisance.
“This feels like an expensive vanity project and not real conservation,” says conservationist Mark Avery, author of ‘A Message from Martha: The Extinction of the Passenger Pigeon.’ “If we ended up with viable populations of passenger pigeons in the wild, that would be amazing, but I don’t think we’re going to get there. There might be some sad pigeons in a cage in a zoo, which is exactly how the passenger pigeon’s existence on earth ended 110 years ago.”
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