What is the significance of the owl and bellman?

In Renaissance England the hoot of an owl flying over one's house was an evil omen, and meant impending death for someone inside. Shakespeare refers to the owl as the "fatal bellman" because it was the bellman's job to ring the parish bell when a person in the town was near death.

Also know, what act and scene is Duncan killed?

In Shakespeare's Macbeth, as is typical in Shakespeare, violence takes place offstage. The audience does not see Macbeth kill Duncan any more than we see Macduff kill Macbeth later in the play. At the close of Act II, Scene 1 Macbeth says: I go, and it is done: the bell invites me.

What are Macbeth's ambitions?

Macbeth: Ambition. Macbeth's ambition is driven by a number of factors including: Prophesy: The Macbeth witches prophesize that Macbeth will become King. Macbeth believes them and the various prophesies are realized throughout the play. However, it is unclear whether these prophesies are preordained or self fulfilling.