It's a long read, but this article talks about the inevitable de-extinction of the Passenger Pigeon (gone since 1914) and possibly wooly mammoth through genetic engineering.

Good idea or no? While obviously a very cool thing, I think it would be a very bad thing. Thoughts?

I'm more curious on why you think it would be a very bad thing. (The passenger pigeon, not the wooly mammoth so much.)

Very bad.

According to the article, within a short time, the pigeons could number in the billions.
It would force out other birds from its ecological niche.
From there, there would be a cascading effect, likely resulting in the unforeseen extinction of many other species.
That is what I feel is the most important danger.
The article quotes someone as thinking it a bad idea because it encourages the idea that we can genetically engineer our way out of environmental disaster. That too, though that is more of a conceptual thing. But introducing a very successful species into an ecosystem is, to my mind, the larger, more immediate problem.

Heck we could hunt them extinction again and again. This would be great. Why should our great grandparents have had all the fun. And pie. Let's eat some pigeon pie!

Ok in all seriousness, ecological disruption is possible but not guaranteed. The biomes are different today than in the previous centuries; there's no guarantee that the population could become stable, let along large. Compare the bison. There is no risk of million-strong herds reforming in my lifetime.

The risk is clearly non-zero, but who knows how big it is? Or on what time frame.

Even with no risk- very bad.

Jurassic Pigeons in the Park!

But if you could engineer them big enough so they could actually carry passengers it might me a good fuel saving idea.

That's what I'm talkin' about!

I want dinosaurs!

Or at least that wooly mammoth...

I love the sunflower seeds tied to the top of the car. Hahahaha!!!

Personally, I don't think it would be a very bad thing.

Although, I can see how reintroducing some species could turn out as bad as when non-indigenous species get introduced to new places and they have no predators and they end up crowding out other species. That's usually bad, unless it's us of course.

Pigeon racing is still quite a big sport here in England and they have started using RFID tags today instead of old numbered rings. I have friend who has been in the game all his life. I did not get into it but I know a little about it from growing up with him. A lot kept Pigeons when we were kids but I don't know any now personally, apart from pal who moved to Wales. I have read the article yet but they kept in Pigeon Pens as opposed to the wild. I mean, I can not see that harming other birds.