A Witch's Familiar
in India they symbolize cunning wisdom. but they are not bad omen. the common crow is considered as wily cunning and scheming creature.
Gatekeepers between our world and the world of the dead....the movie "crow" ectually used this symbol.
Also in some cultures they are seen as carryers of bad news, bad omens, or dark spirits.
In Australia they mean a few different things depending where you come from,one crow means its a relative watching over you,two can mean a warning of death,crows also recognize human faces and can sense if your a good or bad person or will remember you and can warn other people and crows when theres a threat around..They have good memories and face recognition.
It's just a warning for when Itachi visits you, he's such a show off
I have heard that when black crow lingers around you they are comming to take your soul...Not that I beleive that but my dad would sit and watch for them and shoot every one he saw...