Flying

When Clockwork Avian comes into play, put four +1/+0 counters on it. At the end of any combat in which Clockwork Avian is assigned to attack or block, remove a counter.

, : Put X +1/+0 counters on Clockwork Avian. You may have no more than four of these counters on Clockwork Avian. Use this ability only during your upkeep.