- Main article: Bai
The title character and main protagonist of the series, Bai is a young, pink-coloured songbird. He lives in Treetop Town and is known for being a helpful member of the community, despite the fact that he is the smallest bird around. Bai is best friends with an ostrich named Mr. O and often gives him advice on how to live life as an ostrich in the Canadian wilderness.
- Main article: Mr. O
Bai's best friend, Mr. O is a tall ostrich with glasses who always wears a blue tuxedo. He is quite intelligent, but lacks common sense - this is why his comrade Bai must guide him through life most of the time. Mr. O is the largest bird in Treetop Town, and possibly the oldest.
- Main article: Tee Kiwi
The main villain of the series, Tee Kiwi (also spelt T-Kiwi) is a green-coloured kiwi bird. Like Mr. O, he is flightless, but this doesn't make them like each other. Tee and Mr. O are enemies, due to one day (about fifteen years ago) when Tee met Mr. O in the playground. This event is never discussed, but can be inferred that Tee insulted Mr. O that day and made them dislike each other.
- Main article: Nerdbird
A background character seen in several newer episodes of the series. He has not spoken in any of his appearances and it is unknown what his personality is like, although it is inferred that he is rather optimistic as he is always smiling. In Hatena chats, Nerdbird has been nicknamed "Nerdbird Oneword" (because his first name is one word rather than two separate words). This is not considered canon information.