Pierre is a large pink bird belonging to Gan Fall.
Pierre ate the Uma Uma no Mi, a Zoan-type Devil Fruit which enables him to turn into a Pegasus or a full horse.
In his normal form, Pierre is a large pink bird with a red polka dot pattern on his body and horn-like ears. He also has bandages wrapped around his torso. When in his hybrid bird-horse form, he transforms into a horse with wings that maintains the pink body with red polka dot design, but with white feathers. His face also elongates to that of a horse's. In a way, he is supposed to resemble a Pegasus.
Pierre mainly served as transport for Gan Fall.
(Source - One Piece Wiki)