Borgia messenger
Borgia Messengers, also known as Borgia Couriers, appear in the game Assassin's Creed II. Upon spotting Ezio, the messengers take flight, performing many free-run actions and acrobatic stunts, such as climbing walls and swinging from posts. If Ezio manages to catch up to one, he can tackle him or simply throw a Throwing Knife at him for a considerable amount of Florins, which is about 1500 florins per messenger. However, if Ezio kills one, his notoriety will automatically increase by 50%. However, Ezio can still get the 1500 florins (or more) if he loots the messenger.
Presumably, the Messengers carry important information for Rodrigo Borgia, as they are called Borgia Messengers.
Interestingly, Guards begin chasing the messenger as well if he climbs onto a rooftop in his flight.
If you intercept one of them, you get the Achievement/Trophy "Mailman" (10G)
To contradict this statement, this player has never seen any evidence of such an achievment.
Unlike Pickpockets, who have a red icon, Borgia messengers are invisible on your map.