Instant, WUG (3) Put X 1/1 white Bird Soldier creature tokens with flying onto the battlefield, where X is the number of attacking creatures.1 "We are born soldiers. The call to battle is a homecoming."
Illus. Matt Cavotta
5/1/2009: An "attacking creature" is one that has been declared as an attacker this combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step.
5/1/2009: Flurry of Wings counts the number of creatures that are attacking as it resolves. It doesn't matter how many creatures were originally declared as attackers that turn. It also doesn't matter who controls those creatures, or who or what they're attacking.
5/1/2009: If Flurry of Wings is cast before attackers have been declared or after combat ends, it won't do anything.