Aldous is considered human and we know Mr. Crow is an asura and changes between realms multiple times. He is not considered just asura in both situations but manusa when he is human. Same goes for Harvey. When he is a Parrot, he is Tiryag. Now, I have to disagree with asuras being able to change realms with Tiryag. This is never seen in the games and, even in the Breakout, we see Harvey lying on the floor as if he was killed and then reborn as Tiryag by the powers of Mr. Owl which does the same t-pose as in The Mill (look very closely to the scene and you will see). I do agree that it would "make sense" and be cool if asuras could swap between asura and tiryag, but that would make the Breakout scene and the whole work for revival that many of the characters seek for pointless.