>>37821395Silly anon, the lore of Decidueye's type is that one day an employee barged into a meeting to tell GameFreak how witty it would be to slap ghost onto owl cause Pueo owls being ancestral spirits.
The artist had already finished Decidueye's design though so to convey ghost, he changed the face. A shame really since the bow could have had the wing bend into place or some other cool and unnatural ghost power.