The messenger goddess Iris alights at Birds 1199 in the city of Cloudcuckooland. She has been dispatched by Zeus to instruct mortal men on earth to maintain their sacrifices in honor of the Olympian gods, not yet aware that the birds, with the protagonist Peisetaerus as their leader, have founded this city as the hub of an empire that aims to wrest control of the universe from her divine family. This, however, she learns from a tense exchange with Peisetaerus, who forbids her passage through the birds' aerial domain.