The Phoenix is on top of the Phoenix's Nest nest, upon completion of the Lava Caves. You can find Bunk Flowers inside the Lava Caves. You will need at least 5 of these (even though there are 6) to make the Phoenix well. It should trigger the event completion when you have enough.
In other languages
|Japanese||トリの好物 (Otori no Daibutsu)||Phoenix's Favorite Food|