From the Super Mario Wiki
Peach's Bird is an item that first appeared in Mario Kart Arcade GP as one of Princess Peach's special character items. The item later reappeared in Mario Kart Arcade GP 2 once again as one of Peach's special character items.
This item consists of Peach summoning a small pink bird to attack her opponents. Thus, it functions similarly to a projectile attack as Peach can summon the bird to be shot either in front or behind her.