flying clockwork avian enters the battlefield with four +1/+0 counters on it. at end of combat, if clockwork avian attacked or blocked this combat, remove a +1/+0 counter from it. x, t: put up to x +1/+0 counters on clockwork avian. this ability can’t cause the total number of +1/+0 counters on clockwork avian to be greater than four. activate only during your upkeep.