Is only temporarily stunned when you hit it with three throw blocks in the final level? Because Mario Wiki says:
But I've never seen any proof the Hawkmouth is revived if you take too long.
The player must attack using the Mushroom Blocks in the vicinity to temporarily stun the Hawkmouth to provide entry into Wart's throne room.
But I've never seen any proof the Hawkmouth is revived if you take too long.