Lucci is one of the five foremen of Galley-La Company’s Dock One. He appears to be a ventriloquist using his pigeon, Hattori, to speak for him. Lucci also shows very impressive skills when he gets into a fight with Paulie and, later on, Luffy.

Not much is known about Hattori, the pigeon that is constantly seen perched on Lucci’s shoulder. It appears to have no special significance. While acting as Lucci’s voice Hattori expresses human body language, matching the behavior of a professional shipwright: constantly insulting and lecturing Paulie because of his reckless lifestyle. Hattori seems to have affection for his emotionless and bloodthirsty master, as seen when he flew to Lucci’s unconscious body. He also seems to leave his master when he enters any sort of battle, returning directly afterwards. Hattori’s name presumably comes from combining the Japanese word for pigeon, hato (鳩) with the word for bird, tori (鳥).

(Source: One Piece Wikia)