Whisperwing Adept

When Whisperwing Adept enters the battlefield, if {w} was spent to cast it, put a 1/2 white Bird creature token with flying and vigilance onto the battlefield; if {b} was spent to cast it put a 2/1 black Bat creature token with flying and lifelink onto the battlefield. (Do both if {w}{b} was spent.)
They carry messages to friend and foe.