I think it would make more sense to simply create a more bird-friendly environment (ie more sustainable development, no hunting, allow for return of wild forested spaces) and if there is a role for a passenger pigeon-like bird it will eventually be occupied by an existing bird species and those with passenger pigeon-like traits will be the most successful.
The passenger pigeon was killed by
1) overhunting - presumably, we can stop that, but we are doing the same thing to fish right now - what reason do we have to believe we would not immediate overhunt pigeons back to extinction?
2) habitat loss - we haven't done anything to address this. If anything in the past 100 years we've made the problem worse. Development is both good and bad, but for preserving natural habitats, we have not really solved all problems (or arguably even prioritized) allowing development in a way which is sustainable in terms of natural resources and does not threaten wildlife habitats.
Could passenger pigeons start over "from ground zero"? If they could be in a lab, I am very skeptical that such populations would survive.
I imagine if Kang and Kodoss ate all the humans and reduced all human works to rubble and poisone, then genetically engineered a bunch of humans and left them on the planet and said "go repopulate". It just would not work.
Birds are intelligent animals, require long developmental periods (with care of their already-able parents) and form complex social networks that allow them to thrive in adverse conditions. http://rstb.royalsocietypublis... Passenger pigeons would migrate 1000s of miles depending on weather patterns, and used decision-making processes we have yet to understand.