Their wings are too tiny to allow them to fly. They guard their posteriors with bones that were gathered by Mandibuzz.
Its wings are too tiny to allow it to fly. As the time approaches for it to evolve, it discards the bones it was wearing.
They tend to guard their posteriors with suitable bones they have found. They pursue weak Pokémon.
It protects its plump posterior with the bones of prey it has consumed. As it grows, it replaces the bones.
It can’t fly yet and must wait until its wings have developed more. Since it’s still at a playful age, it hops around friskily.
— Pokédex entries (via PokeAPI)