This image is the epitome of Marco and Celia. This image shows that Marco and Celia cannot love one another in the physical world, they must fade into birds in order to fly away. The fact that the man is turning into birds represents the end of the novel, when Celia and Marco find their wings and make their own decisions.
The fact that the bird is in a person's hand represents Celia and Marco. They were birds able to fly, but stuck to the lives Prospero and Alexander chose for them. Marco and Celia were in Prospero and Alexander's hands.