Bowser reacted to dying with nonchalance. He merely said "Showtime." as a 1-UP Mushroom sound effect rang through the air, or perhaps only his mind. Death wasn't a stranger to him, he had gone through it around 50 times already in this world alone, and he'd sustained so, so many mortal injuries in his home world. Fortunately he'd come back each time, sometimes as a skeleton, but he never stayed down.

"How many times can that bird thing do that?" he asked, deciding that was all he could do. Bahamut was much farther than any of Bowser's attack could reach. So rather than take any additional action he simply observed the situation.