Final answer:
The theme in the three swans is the exploration of human existence through love, allowing the poets to explore deeper aspects of the world.
Step-by-step explanation:
The theme in the three swans can be identified as the exploration of human existence through the lens of love.
While the poets of the sixteenth century may all be writing about unrequited love, they are actually using this theme to delve into deeper aspects of the world, such as religion, the self, relationships, and the nature of love itself.
In essence, love becomes a vehicle for exploring these larger ideas.