Birds have feathers. And birds fly. But the feathers are not to aid flight. And I’ll prove it.
Dinosaurs evolved from reptiles. And birds evolved from dinosaurs (theropods). After all that evolution, much is still similar. Birds still have beaks and make nests and lay eggs in them. But birds and theropods have a new body shape (their legs that go straight down from their bodies), feathers, skin, and they lay hard eggs.
Compare photos of a chicken and a veliciraptor. Then compare their skeletons. There is not much difference at all. It is like comparing prehistoric and modern crocodiles.
The flying animals in dinosaur times did not even have feathers, but the flightless therapods did. And most modern flying animals do not have feathers.
Some birds have evolved feathers with special aerodynamic properties. But then bats have evolved skin, and insects have evolved wing-tissue with the similar properties.
Birds also evolved special bone structure to aid flight. Saying feathers are for flight is like saying bones are for flight.
Theropods evolved feathers, but they did that millions of years before they started flying. Many of them never evolved to fly at all, including many extinct dinosaurs and many living birds. The ability to fly is distinct from the bearing of feathers. There is no connection at all.
There is some contention in the world of paleontology regarding the evolution of dinosaurs into birds. They suggest instead that there is some form of common ancestor like (but not THE) the Yi qi. Among other evidence for this, animals don’t evolve the capability for flight “ground up” but rather “trees down.” Evolution happens to get an advantage or fill a particular niche, but for a ground dwelling creature simply jumping and landing has no benefit in aiding escape from predators as you have to land, however for a tree dwelling creature like flying squirrels, some lizards, and a snake or two who already have the height advantage being in the tree to glide to another tree to evade capture, it is creatures such as these that have an evolutionary advantage in gaining flight. A ground dwelling creature would be better served (and have an easier time) evolving to climb the tree to evade predators than to jump and simply fall into open jaws. If you’re interested in this sort of thing may I reccomend to you a Dr. Hal Robbins of The Church of the SubGenius, on his show Ask Dr Hal on Radio Valencia he talks about this sort of thing rather frequently among other things he likes, here’s an episode which goes into better detail about this than I can (you may have to skip through it to find the relevant part though, heads up.)
https://www.radiovalencia.fm/podcasts/?episode=39394
I hadn’t thought of that.
But for a ground-dwelling predator, there would be an evolutionary advantage. If they can jump higher and further by flapping, they can catch flying prey more easily. The ability to turn while in the air, by flapping, would be an even more important evolutionary advantage for a predator.
What you said is a new perspective for me. I’ll think/research a bit more about it.