Does Not Answer

My 13 month old son does not answer to his name all the time. But when you say, for example "look what Mommy has" he will answer.

He walked early, talked early, and continues to do so. His vocabulary includes, mom, dad, ta-ta, quack-quack, up. He also understands when I tell him it's bath time. He will then run to the tub. When its supper time he will run for his high chair. Is this something I should worry about?