This poor little creature is supposed to have somehow survived a thousand generation process during which it had neither functional arms, nor functional wings, during which it had enough flight feathers to look weird and be laughed at, but not enough to fly, a light enough bone structure to be kicked around on beaches, but not light enough to fly, and was generally an outcast, pariah, ugly duckling, and effortlessly free meal for every predator which ever saw it for 1000+ generations before it ever succeeded and flew.
An idea of how hard it would truly be for "proto-bird" (TM) to make it to flying-bird status can be gotten from the case of the escaped chicken.
Consider that man raises chickens in gigantic abundance, and that on many farms, these are not even caged. Consider the numbers of such chickens which must have escaped in all of recorded history; look in the sky overhead: where are all of their wild-living descendants??
Why are there no wild chickens in the skies above us???
A flying bird requires a baker's dozen highly specialized systems, including flight feathers, wings, a special light bone structure, specialized flow-through design hearts and lungs vastly more efficient than ours, specialized tails and balance parameters, and a number of other things. Now, you can imagine the difficulty involved for something like a dinosaur which did not have any of these things to evolve them all, but the feral chicken
In other words, if there's any chance whatsoever of a non-flying creature evolving into a flying bird, then surely, surely the feral chicken, close as it is, could RE-EVOLVE back into being a flying bird. They're only missing the tiniest fraction of whatever is involved.
They've got wings, tails, and flight feathers, and the whold nine yards. In their domestic state, they can fly albeit badly; they are entirely similar to what you might expect of an evolutionist's proto-bird, in the final stage of evolving into a flight-worthy condition.
According to evolutionist dogma, at least a few of these should very quickly finish evolving back into something like a normal flying bird, once having escaped, and then the progeny of those few should very quickly fill the skies.
But the sky holds no wild chickens. In real life, against real settings, real predators, real conditions, the imperfect flight features do not suffice to save them.
In real life, if you ever lose the tiniest part of some complex trait or capability, you will never get it back. In the real world, if you lack the tiniest part of some complex trait or capability, then, other than possibly via some genetic engineering process, you will never get it.
Thus we see that "proto-bird" (TM) not only couldn't make it the entire journey which he is supposed to have, he couldn't even make it the last yard if we spotted him the thousand miles minus the yard.
The basic question is: How in hell is some velociraptor supposed to make it the thousand miles, if history proves that a creature which amounts to the final stage of such a development cannot make it the final yard of such a process?
This kind of thing. We have little velociraptor-like critters with feathers all over, including long maneuvering-vane feathers on their foreclaws. That's what I mean about easing into flight. Archaeopteryx has a skeleton not much removed from that same little critter--still with teeth, foreclaws, and a long, bony tail but with much better feathers. You don't have to be a stinking detective to put it together.
As for chickens not radiating into every conceivable ecological niche, it's a poorly adapted latecomer unless a particular niche is empty for some reason. That's why the fossil record shows long periods of stasis, punctuated by lots of adaptive radiation following every big die-off. That's when a lot of niches are empty