At its absolute worst, it's a 3/3 Flying Vigilance for 4. That's already playable in Limited. But most likely it'll mess up the combat math real good and impact the board immediately once it drops. This is really good for a Common, and I've seen people run much worse in Kangee, Aerie Keeper Bird Tribal.
I'd like to remind everyone that this happens before the declare attackers step, so not only vigilance works and that your opponent knows exactly where the buff lands. Battle-Rattle shaman but in white