They went extinct 100 years ago, or so. They seem very similar to existing pigeons…so their DNA probably is very close. So, assuming you have usable DNA (from a museum specimen), what next? You take existing pigeon DNA, and insert the passenger pigeon genes into it, and clone the bird. Would it be withing current capabilities?
Somebody will come by with a more informed response, but I believe part of the reason why they went extinct was that they somehow required massive flocks to thrive.
Once their numbers dropped below some key threshold, the remaining birds weren’t able to compete with other birds.
Therefore, I think you would need to breed a large number of birds before they could be released. Not an insurmountable barrier, but a significant one.
Please note that I am no expert and this could be completely wrong.
Since they didn’t go extinct that long ago there’s some chance that DNA can be extracted from remains and possibly used with extant pigeons to produce a bird similar to the Passenger.
I can see the Steven Spielberg movie now, with the Richard Attenborough-like millionaire welcoming the Inspection Committee to his island:
“Welcome, my friends, to Passenger Pigeon Park!”
All goes well on the tour, which shows an animated film about cloning Passenger Pigeons from “Martha’s” DNA, filled in with chunks from modern pigeons, going past an incubator where robotic arms turn the eggs, and we see an actual chick being born.
But things go wrong on the tour when a storm shuts down the electrical grid, and pigeons escape their electrified aviary.
What happens next? I don’t know. we discover the downside of restoring an extinct species. Maybe tree branches break under the weight of all those birds. Maybe they all release their poop in unison. Maybe the Computer Geek who rigged the fences finds out the hard way that some passenger pigeons spit poison – and go for the eyes. Maybe it turns out that passenger pigeons are possessed, and we’re subjected to flocks of Red-Eyed Pigeons From Hell acting with a single will.*
It will make Alfred Hitchcock’s The Birds look tame.
*“Pigeons from Hell” was actually the title of one Robert E, Howard story, included in many horror anthologies. It IS a good story, but I find the title hilarious, considering the fate of my aunt in a park once. Or of Mel Brooks’ character in one scene in the movie [High Anxiety.
Probably from The Pretenders’ “Back On The Chain Gang”:
A circumstance beyond our control, oh oh oh oh
The phone, the tv and the news of the world
Got in the house like a pigeon from hell, oh oh oh oh
Threw sand in our eyes and descended like flies
Put us back on the train
Oh, back on the chain gang
So long as they stay out of the park, they should be ok.
I wish Dr. Hrad and his team good luck in this scientific venture for the ages.
He’s just a ho.
No, you’re on the right track. I am sure Colibri will come by and give us the Straight Dope, but the Passenger Pigeon was one of a number of species that wont breed unless there are lots of them. They also need massive hardwood forests.
Potential de-extinction[edit]
Some have suggested cloning the passenger pigeon in the future.[108][109][110] De-extinction efforts are now underway to revive the species by extracting DNA fragments from preserved specimens, and later, using band-tailed pigeons as surrogate parents.[111] A significant challenge to an effective de-extinction effort is the fact that the passenger pigeon was a very social bird known to form flocks of millions. When their numbers dwindled to a few thousand, the birds stopped breeding; it is likely that more than a few thousand birds would have to be created for a de-extinction effort to be successful. Also, the pigeons that would raise them would be a different species, with differing mothering techniques.[112]
Even if it could be done, would we want it to? Here’s a quote from a short piece mentioning a book about them:
"…passenger pigeons, traveling in flocks so massive as to block out the sun for hours or even days. The down beats of their wings would chill the air beneath and create a thundering roar that would drown out all other sound. Feeding flocks would appear as “a blue wave four or five feet high rolling toward you.”’
The book itself is called “A Feathered River Across the Sky”:
What city, town, or farm wants to see that show up?
I’m not making fun of the OP, but I glanced at the title and thought that Ho Hrad was some Chinese geneticist or something.
Or, most American downtowns where the idiots feed pigeons. 
His mom was Chinese. His dad is Serbian.
You’ll have to excuse ralph, he has a Type O Personality.
It can’t have been much fun to be under it, either.
Hence the term: shit storm. 
From the sound of it you could kill at least half a dozen birds with one stone. Maybe a hundred or more if you had a catapult. So there’s that.
I’ve read descriptions like that before. How much of that is exaggeration? How big were those flocks, in reality? Because it sounds like what’s being described would require massive amounts of food.
Whole forests were denuded of nuts, etc.
Honestly, the PP could not have survived into modern times.
This scene?