Final answer:
Upon hearing the report of Birnam Wood moving, Macbeth is initially incredulous but then resolves to fight to the death as the enemy advances.
Step-by-step explanation:
When Macbeth is informed by a messenger about Birnam Wood, he does not believe the report initially, as it seems impossible based on the prophecy he received from the witches. Only when he confirms that the soldiers are camouflaging themselves with branches from Birnam Wood and advancing towards his castle does he decide to fight to the death. Despite his shock, Macbeth decides to face the forces moving against him, which aligns with his earlier determination to fight against what he perceives as fate.