>>28206659This is a funadamental misunderstanding of what Flying represents. Flying means the Pokemon has wings, or another instrument that is a part of its body that acts like wings.
Pidgey: Bird (Normal) with Wings (Flying)
Charizard: Fire-animal (Fire) with Wings (Flying)
Butterfree: Arthropod (Bug) with Wings (Flying)
Zubat: Poisonous-creature (Poison) with Wings (Flying)
Gyarados: Water-based creature (Water) with fins that act as appendages that allow it to fly (Flying)
Noibat: A Bat (Normal) or Sound-based creature (no established type) with Wings (Flying) that is also a Dragon (Dragon). In the first case, Normal dropped just so it has two types.
You get my point. Flying has *nothing* to do with being a bird. That most Flying types are birds is merely a coincidence, much like most Water types being fish (but some mammals), or most Bug types being insects (but some arachnids). And despite what
>>28206685 says, the Pokedex states that Doduo has wings; that is how it is able to Fly igname.
Tornadus: Not a real animal or covered by any other type, but it has its cloud appendage for flying, so it is pure Flying.