Hattori is a dove owned by Rob Lucci.
Appearance
Hattori is a white dove and is always seen wearing a bright red tie when Lucci disguises himself as a shipbuilder and turns black afterwards. When the CP9 group returned to Enies Lobby by sea train, Hattori was seen wearing a light green coat identical to his master.
Characteristics
Why Hattori could be with Lucci is unknown given his reputation as a heartless killer, but Lucci has had it since he was a child. He doesn't seem to be afraid of Lucci and is very loyal to him, because he stays close to his master even in dangerous situations like Buster Call. He then tried to bandage his master after fighting Luffy. When not fighting, Hattori usually perched on his master's right shoulder.
Hattori was very helpful to Rob Lucci during his disguise, because the CP9 agent had to express some emotions to mingle with the residents while Hattori was acting as his "ventriloquist" puppet. This allows Lucci to socialize enough while he keeps his appearance. After the disguise ends, Hattori turns into an ordinary dove, but sometimes he behaves like a human like drinking from a cup.
Ability
Hattori has no fighting ability. When Lucci fought, he tended to fly out generally drifting around like a bird of prey until the fight was over. He seems to be very intelligent because he can imitate human behavior; like acting as Lucci's ventriloquist and moving his wings like the behavior of a human arm, and facial expressions. Can Hattori really understand human behavior or this is just his bond with Lucci with no certainty.
During Lucci's disguise in Water 7, Hattori functioned as his master's spokesperson and did several other expressions, such as making wing movements that really matched what the master meant without having to do anything.
Enies Lobby
After the CP9 mission ends, Hattori returns to being a regular dove. He looked with Lucci when he returned to Enies Lobby by sea train. Then after Lucci fought Luffy, Hattori flew close to his master carrying a bandage.
CP9 Independent Report
After the Buster Call attack, he and the rest of the CP9 escaped. They arrived at St. Poplar where agents work as street artists to pay for Lucci's treatment. Hattori always seemed to be with other agents because he was later seen eating with Kumadori. He was seen in the window when Lucci woke up, looking happy that his master had recovered. After that, he returned to perch on his master's shoulder as usual.
Source : WIKIA ONE PIECE