Saturday, March 22, 2014

The Passenger Pigeon: Should it be Brought Back?

It is often said that the passenger pigeon, once among the most abundant birds in North America, traveled in flocks so enormous that they darkened the skies for hours as they passed. The idea that the bird, which numbered in the billions, might disappear seemed as absurd as losing the cockroach. And yet hunting and habitat destruction pushed the animal to extinction. Martha, the last known passenger pigeon, died in 1914 at the Cincinnati Zoo.

Plans are afoot to bring back the bird by using a weird-science process called de-extinction. The work is being spearheaded by Ben J. Novak, a young biologist who is backed by some big names, including the Harvard geneticist George Church. The idea was recently promoted at a TEDx meeting in Washington and is being funded by Revive and Restore, a group dedicated to the de-extinction of recently lost species. (Other candidates include the woolly mammoth and the dodo.)

Novak’s idea takes a page from “Jurassic Park,” in which dinosaur DNA was filled in with corresponding fragments from living amphibians, birds and reptiles. Working with Church’s lab and Beth Shapiro, an evolutionary biologist at the University of California at Santa Cruz, Novak plans to use passenger pigeon DNA taken from museum specimens and fill in the blanks with fragments from the band-tailed pigeon. This reconstituted genome would be inserted into a band-tailed pigeon stem cell, which would transform into a germ cell, the precursor of egg and sperm. The scientists would inject these germ cells into developing band-tailed pigeons. As those birds mate, their eventual offspring would express the passenger pigeon genes, coming as close to being passenger pigeons as the available genetic material allows.

The process is not the same as cloning. Novak’s approach would use a mishmash of genes recovered from different passenger pigeons, resulting in birds as unique as any from the original flocks. Most pigeons mature and reproduce quickly enough that the de-extinction process could be completed in less than a year. Producing a flock large enough to release into the wild would take at least another decade.
Novak says he is confident the procedure will work. “Essentially, the genomes of the band-tailed pigeon and the passenger pigeon, I think, will prove to be similar enough to easily convert one to the other,” he said. In fact, he says, “making the passenger pigeon genome right now will be easier than making the first living passenger pigeon hatch from an egg.”

Experts say there is little question that re-creating the pigeon is technically possible. Indeed, the genome of the woolly mammoth has largely been sequenced using elephant DNA as a scaffolding. Complete, working genomes of dogs, sheep, horses, cows and other species have been artificially inserted into egg cells to produce living organisms.

But the project still faces many challenges, among them the contamination of much of the DNA specimen.

The hundreds of passenger pigeons in museum collections have been exposed to heat and oxygen. Specialized equipment would be used to identify the surviving fragments of DNA and reassemble them into working genes. It’s a painstaking process that could take years.

But the larger problem, say some scientists, is that even if the passenger pigeon is re-created, it’s unlikely to be viable as a species in today’s ecosystem. Novak’s plan is to breed the first new generations of the bird in captivity. But eventually he hopes to release the animal into the wild.
Such a proposition, some experts say, poses a number of fundamental problems: There is some question as to whether today’s forests can support a restored passenger pigeon population, and its nesting behaviors make the bird particularly susceptible to dying out again.

“Much of their breeding and wintering habitat is gone,” says Scott C. Yaich of the conservation group Ducks Unlimited, and the animal’s primary breeding-season food — beech mast, the nuts of a beech tree — is limited.
Altered landscape
The birds “simply couldn’t be restored to a landscape that is so radically altered from the one to which they were uniquely adapted,” says Yaich, director of conservation for Ducks Unlimited.
But Mark Twery, a research forester at the U.S. Forest Service, says that though beech bark disease has reduced beechnut production, “the overall quantity of forested habitat is likely to be ample to support a large enough number of pigeons for a viable population, even should people be able to restore the species.”

Other experts say that given the nesting behavior of the passenger pigeon, releasing a handful of birds into the wild would be a losing proposition.

The mainstream view of passenger pigeon ecology is that they used a reproductive strategy called predator satiation. The recent cicada invasion is one example of this strategy. Each cicada is individually easy to catch in its slow, bumbling flight. But there are so many millions of cicadas in a spot at one time that they are able to finish mating and laying eggs before predators have had time to eat all of them. If only a few thousand cicadas emerged at once, then most of them would probably be eaten before they were able to reproduce. In this way, the cicada’s survival depends on showing up in hordes.

Flimsy nests
Passenger pigeons succeeded through a similar sort of mob rule. Individually, their behavior was borderline reckless. They built flimsy nests, often dangerously low to the ground. The nests were built so hastily that when bad weather would slow down construction, a female would sometimes be forced to lay her eggs on the ground. When the young were ready to leave the nest — after only 14 days of development — they would spend their first few days on the ground, vulnerable to any hungry predator.
Passenger pigeons could get away with such behavior because of their incredible numbers. When a flock arrived at a nesting area, predators could gorge themselves for weeks. Each pair of nesting pigeons would produce two eggs, at least one of which usually ended up on the ground. But even with the constant work of foxes, bears, possums, raccoons, hawks, eagles, snakes and other meat-eaters, enough of the young pigeons survived to fly away.

This system works great with a flock of 5 million birds. But according to Kirk Mantay, a biologist specializing in habitat restoration, if only a few thousand pigeons show up, the whole system falls apart.

“If you put 5,000 out there, even with good habitat, they could all still be gone in a few decades unless you could exclude the predators somehow and make sure that they nested right where you wanted them to go. You just couldn’t make enough birds for it to work.”
A handful of nests and fledglings might escape the notice of predators, but as soon as the colony grew to a few dozen nests, the noise and scent would bring those predators in to feast on easy meals. You would need to skip ahead to millions of birds for the predator satiation strategy to properly work.
Still, “I believe the passenger pigeon will survive because we have people committed to its survival,” Novak says, citing the reintroducton of the condor into the wild in California. In that case, the birds, on the verge of extinction, were bred in captivity, then gradually released beginning in the 1990s; there are now about 200 living in the wild.

Would a commitment to its survival be enough to sustain the passenger pigeon? A few specimens living in an aviary would be a historic accomplishment. But an effort to put the passenger pigeon back into the wild would be challenging at best.

“Habitat restoration is hard to get right for species like turkey and quail that we know about,” says Mantay. “How long is that going to take with something we can’t study in the wild first?”
There may be other species that could be resurrected, animals that can survive in smaller numbers with less habitat. The Carolina parakeet might have a chance, with federal protection. The woolly mammoth could do very well in a herd of a few dozen within a large park, living at least as wild as bison in Yellowstone. As for the passenger pigeon, science may permit us to mourn it all over again.

Landers is the author of “The Beginner’s Guide to Hunting Deer for Food” and “Eating Aliens.”

© The Washington Post Company


Anonymous said...

Personally, I don't see the need of bringing this species back into the wild. There was a reason that they went extinct in the first place, their species did not have the skill enough to stay alive in the wild, so why do we feel the need to bring them back? To me, it is survival of the fittest, and species extinction is part of the process of evolution. Unless humans, by deforestation or other causes, cause an organism to go extinct, I don't feel like there should be a stress on bringing that organism back.
As a side, if we release thousands upon thousands of these bred animals into the wild, who can say that we wont interfere with the natural processes of nesting in ecosystems where species already exist? It could lead to other problems in other species that may lead to extinction on another end. Like the article said as well, the reason that they survived was because there were so many of them, and if we cannot even create enough of them to give them a fighting chance, what is the point?

Leanna Molnar

Gina May said...

It’s pretty astonishing that something such as extinction, thought of as irreversible and permanent, might now in fact be able to be reversed. Although it would be an amazing scientific breakthrough to be able to bring an extinct species back to life, the idea of de-extinction raises far too many concerns for me to be onboard or support it this early in its development. The idea that scientists would be genetically modifying a dead species and creating a sort of new hybrid that is not the original animal seems a bit risky and dangerous to me. Also besides the process being extremely expensive and time consuming my biggest concern would revolve around creating a sustainable environment for the relived species. In my opinion a species should not be brought back until we can ensure that they will be released into a viable environment. Would it be cool to see a wooly mammoth or passenger pigeon in the zoo? Sure. But it’s not fair and I think the entire process would be a complete failure if they would be bringing back certain animals just so that people can watch them like some sort of freak show.
Although I seem to have shifted more towards the cons involved with de-extinction, I am not entirely against it. I am still very impressed by the idea/process; I just don’t see it as being a completely necessary one.

Gina May

Anonymous said...

I dont blame scientists for being so eager to reintroduce lost species. It is remarkable in every sense however I don't thing anything good would come as a result. The reintroduction of the carrier pigeon has little hope in my eyes. Those birds resulted from thousands of years of evolution by natural selection. A process completely relying on the current surroundings and environmental pressures. Sticking an animal in a new environment will only cause a second extinction. This could be true for the carrier pigeons or other species due to over consumption by the carrier pigeons. Fixing the damage we have done must be done in a natural way without the disturbance of man. I believe any other method would only complicate and greatly disturb the current web of life. I am greatly enthused by the thought of seeing species I have yet to see however the risk in my eyes is not worth.

Dillon Addonizio

Leah DeEgidio said...

Before reading this article I did not know de-extenction was possible. This is remarkable, as I would think anyone would agree, however, the second half of this article convinced me it is not a plausible plan. The nesting problems seem to be the downfall of this particular species. The population would not be anywhere the same as it was pre-extinction and if it is that easy for predators to get to the eggs, this species will never achieve the population numbers it previously had. The ecosystem has changed since passenger pigeons were a thriving species and I think it is naive to think that they can be reintroduced to the world without any negative impacts.

Anonymous said...

In my opinion de-extinction should not even be an option. Humans destroyed the habitats of these birds like we have so many other creatures and now we are trying to right our wrongs with the same technology that put us in this position. If we had lived sustainably and responsibly within our limits we would not need to spend time trying to bring creatures back. Instead of spending money and manpower on bringing creatures back into a world we have made unlivable for them we should put our efforts into rehabilitating the destroyed habitats of threatened and endangered species.

-Haylei P.

Nick Sollogub said...

What this article fails to ask is why. Why should we bring back an extinct bird? What purpose does this serve other than allowing people to meddle in things that they don't know about. Let's say that they do De-extinct the passenger pigeon, then what? Their habitat is no longer the same and they went extinct for a reason, so wouldn't that happen again. Even if they didn't go extinct quickly and were able to survive, what would the repercussions be. Would they change their ecosystems and have negative effects? Yes I think that it is impressive that humans have the technology to be able to bring back species or something very similar to an extinct species, but I do not understand its purpose. Is it supposed to make people feel better? I just don't understand it.

Apoorva said...

The thought of bringing back something back from extinction and the rate of possibility is astonishing. It shows how far science and technology has come in the modern world. However, I do not see how bringing back these Passenger Pigeons is in anyway going to help the environment. There have been many other species of birds such as the famous Dodo Bird which became extinct, yet we don't see anyone taking the effort to bring those back with the use of DNA and specimens, so why are these birds in anyway different?
The behavior characteristics of these pigeons seem to be reckless enough that even if the scientists after all their years of research and practice will eventually end up wiping themselves out again. Also, from the article, I understand that the only reason they could afford to behave like that is because of their vast numbers so bringing them back would be in smaller numbers and thus the rate of survival will be minute.
Theres also a question of adaptability. Will the birds be able to survive in the present conditions that were different to when they were still in great numbers?
I think there's a lot of factors to consider when talking about bringing a creature back from the dead and also the necessity of bringing the pigeons back.

Apoorva Muthukumar

Dylan Hirsch said...

Reintroducing a species to the wild that was once extinct is controversial at best. Many, if not most, of the natural life has been eradicated with the massive expansion of the human species. From the massive industries based on the trade of fur and hides, the use for whales and there oils and bone, for birds for food, etc., man has plundered the natural world in an irreversible way. Many species can not escape the philanthropic extinction. The question is of the importance of having a bio-diverse natural world. Introducing the pigeon back into the wild would only cause a more biodiverse ecosystem, and would restore some balance and stability to these natural systems. Humanity can either continue to consume the natural capital (in the case living animals), or move to the preservation of biodiversity in the wild.

Melis Temelli said...

Although the idea to bring the passenger pigeon back to life is an interesting one, I do not think that this will lead to fruitful results due to a number of reasons. Firstly, we do not know if this species will survive when the birds begin to live in the nature. The nature as we know today might be coded in a very different way compared to the nature more than a century ago. Secondly, there is never a guarantee that the passenger pigeon will be the same bird when it is brought back to life through some genetical modifications, because the conditions surrounding these birds will not be the same. Thirdly, we do not know if these birds will survive and whether they will have positive or negative effects of the environmental situation surrounding them. For instance will there be a risk of extinction for other animal or plant species if passenger pigeons survive. Lastly, the step to revive passenger pigeons will not be realised in line with natural evolutionary process. As a result, the inclusion of the species artificially could harm some natural evolutionary processes. Although I do not support the idea for passenger pigeons, there is more space for the same idea when certain species are really needed for survival of human beings or other life forms. So, I am looking forward to see the results of this project, despite the fact that I do not support reviving passenger pigeons.

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