Text (IN+errata): 2/2, Flying. ; {U}: ~this~ gains shroud until end of turn. [Oracle 2007/05/01]
You can play the shroud ability in response to this card being targeted by a spell or ability. If you do so, then the spell or ability will fail to do anything to this card since this card will now be an illegal target. [Invasion FAQ 2000/10/03]