This was the technology/magic that had made humanoid creatures out of nearly every animal species on the planet with intelligence and language equal to humans (though completely without the socially engineered sense of empathy, morality, ethics, etc, that said eating an intelligent being you could have a conversation with, or eating your young to get back the energy used to make them rather than give it to a predator, etc was wrong). The mass had come from effectively nowhere. That was not how science worked. And the amount of energy needed to create that much mass would been incomprehensible to modern science.
So bending the laws of aerodynamics, to enable anthro flying birds to actually fly, was not precisely impossible. One of the slightly more rational scientists of the green terror group that had created the anthro disaster had indeed been programmed/enscripting a subroutine/sub-rune, explicity to grant flying bird species the lift needed to get themselves off the ground. In fact, that fact their bodies were explicitly MADE FOR FLYING, and suddenly being too large for it to work, was dimly recognized as dooming them to an insanely huge disadvantage, as the muscles, bones, and body shapes designed for one particular task would suddenly be unable to perform that task, and be rather sub-par at other applications.
But police had been closing in, and it was excused as an 'unfair advantage' for them to have in the new world (never mind that of other races).
So for the last 230 years... Bird Tribes had been... barely above Scavengers in terms of the new world's pecking order. The ones who could produce eggs on a regular basis were kept as prey. The ones who were nominally predators sound the talents and traits that had served them so well before the end of the world were suddenly of minimal use, and with the chaos and death around them, they didn't have the time or resources to adapt. Flightless birds, of course, ones who had been flightless BEFORE the change that is, were naturally much faster to adapt since their bodies were already designed for such things, and were higher on the pecking order than the rest of their kind.
However... that researched had been dedicated to an small AI, that over the last two centuries on an old combination of solar, wind, thermal, and scaled down twin fusion-fission reaction... had continued to function and finished the research. But with the devastation that followed, there were none of the terror group that had spawned this nightmare and the suicide of all of human accomplishment. So there was no one to take advantage of this AI had been shielded from the wiping of all other electronic human records and equipment... Thankfully, being closed off DID mean that all its equipment was technically intact. It had been running on minimal power before, but now it took the risk of restoring full power, and to now complete its purpose to grant flight to those who had been taken away from.
Of course the real problem was that it didn't exactly have a neon sign that read 'here birds, free working wings.' And it wasn't like Birds had settled right on top of where the AI and its automated lab had been buried. But did have a few tricks up its sleeve, it had been thinking for a very long time, including using equipment in ways that it hadn't been intended for.
Birds couldn't fly anymore, but instincts didn't vanish in the scant course of over only 200 or so years... And birds still felt the instinct to migrate south... Even if they didn't quite understand what they were supposed to be doing.
Some manipulations of the local magnetic field of the planet, and boom, instant bird attraction ray.
Zariel, a young falcon lad, had been traveling with a caravan when they had gotten lost and separated... as fate would have it... Zariel was the first to arrive. Of course the place by then was well overgrown, and the entrance had been buried and everything else, so Zariel would have been felt compelled to go on but had no way to.
But the still working manipulator tools it had (not that many), to handle equipment that hadn't been automated, (a final gift of its creator before her end, and she'd also given explicit permission to use her corpse for research after she died, no, the AI did not hurry that last part). And it used those tools to open up and break away as best it could a path that the young Zariel could get through. Zariel had no idea what drove him on, only understand that he HAD TO!
The things inside confused him to no end, having no idea what the things and machines were! Getting inside the AI's lab, past security sentries long since died or rusted... his instincts SCREAMED at him to get onto a platform glowing blue with an identical glowing blue circle above it.
Zariel did as his instincts instructed... and a blue light envelope him...
The AI was intelligent enough to know that asking every Avian to come in here for an upgrade would have been absurd. So the upgrade was made to spread to every Avian that the first came into contract with, and they came into contact with, and on and on.
Zariel felt his wing grow larger... stronger... not absurdly so, and he could still use them to manipulate tools, but now... he flapped his arms with instincts his people hadn't understood for 200 years, and he hit the ceiling.
"OW!"
'Sorry about that.'
"Wha... who are you?"
Screen flickered on, showing a flicking green face made of typography symbols. The AI's creator would have been shocked, he had never programmed that into it, let alone apologies or empathy or concern, but the AI had had a long time to learn. And had plenty to do in its spare time waiting for lab results.
"Are... are you a ghost?"
'You had to have been alive to be a ghost. Nope. I'm an AI.'
"Aeee-Eye what's that?" Zariel asked sincerely confused.
'Ya know, something that is constructed on a computer to think like a person.'
"What's a computer?"
'Geeze. Okay, we're gettng off track, let start again, Ahem!
'Yo, the gift of flying is yours, spread it to every avian you touch, well, it'll work for most, I couldn't ever figure out how to get it work with penguins or ostriches.'
"What's ... flying? You mean like insects? These wings can't buzz. What's a penguins? What's an ostriches?"
'Ah, I see that I'm gonna have to teach a couple of things first, don't worry, grab a protein bar over there, don't worry they're still good, thank modern industry, well, more like ancient industry now.'
"Industry? What's that?"
'A lot to teach you. I have a full dictionary programmed into me, but my education program is related to bird autonomy, relative state matter revision, some forms of alchemy, genetic engineering, and some of the more basic 'magics' I guess was the best name they could come up with it. But that doesn't really relate to my function kid, so let me go over the basic of flying with those now working wings of yours.'