LitCharts assigns a color and icon to each theme in Macbeth, which you can use to track the themes throughout the work.
Ambition
Fate
Violence
Nature and the Unnatural
Manhood
Summary
Analysis
Duncan, Malcolm, Donalbain, Banquo, Lennox, Macduff, Ross, and Angus arrive at Inverness. Duncan comments on the sweetness of the air. Banquo notes that martlets, a species of bird that usually nests in churches, have nested in the castle.
It is ironic that Duncan thinks the castle where he'll be murdered is beautiful. The beauty of the castle, and the way it seems blessed by nature with sweet air and nesting birds, also shows what Macbeth loses when he gives in to his ambition to commit the unnatural act of murder.