Zelda II: The Adventure of Link/Thunderbird
From Red Candle
Notes on Thunderbird:
Thunderbird ignores all upstab and downstab hits. Don't bother trying.
It's important to keep moving so the fireballs spread out. The fireball pattern doubles when you get him down to half health.
If the room gets hectic, you can move to the right edge of the screen, lure Thunderbird mostly off screen, and reset the pattern.