Long, long ago, Athenians are very litigious and are weary of all sorts of customary taxes and tithes. Pisthetaerus and Euelpides, wanting to escape it all, leave their city-state to search for a utopia where they can live in serenity. In the woods, they come to the home of the Hoopoe bird. Once a person named Tereus, he was turned into a bird by Zeus as punishment, and so is versed in both the affairs of humans and the customs of birds. The Hoopoe recommends many places for the two men, but no place satisfies them, so they decide to live with the birds, where they would enjoy freedom and leisure. Pisthetaerus presents a plan to the Hoopoe bird, telling him that the birds occupy the place between men and the gods. If birds were to build a city-state in their own territory, they could block communication between them. The aroma of the burnt offerings made to the gods would not reach the heavens and the gods would beg for mercy out of hunger, and be forced to serve the birds. The Hoopoe accepts the proposal and summons a meeting of all birds.   

The Chorus, made up of birds, come to the forest at Hoopoe’s beckoning, and upon seeing the humans, their natural enemy, they begin attacking Pisthetaerus and Euelpides. The Hoopoe pacifies the birds, and gets them to listen to Pisthetaerus’ plan, who explains that birds are the original rulers of the world and that all people should make sacrifices to them. Then gods appeared and replaced the birds, after which people lost their reverence for birds. If birds had their own kingdom, they could take back their rightful place as rulers of the world. The birds were delighted to hear this and accepted Pisthetaerus and Euelpides into their community. The two men grow wings and, laboring alongside the birds, build high city walls. They name their city-state Nubicuculia, or cloud-cuckoo-land.

Before construction is completed, they receive uninvited visitors; a poet, a prophet, a geometrist, a surveillant and a statute-seller. They shower Pisthetaerus with flattery while courting all sorts of favours. But he sees through their trickery and drives off each opportunist one by one. The goddess Iris shows up in Nubicuculia with a message from her father, Zeus, saying the birds are preventing, the smoke from humans’ sacrifices from reaching the heavens and the gods are starving. Pisthetaerus sends Iris away with a message for Zeus, saying the birds are the true rulers. Another round of visitors follows, pleading to join their city in the clouds. This time a rebellious youth, a dancer and a false accuser. They demand wings from Pisthetaerus, wanting to become birds, but since their motives are impure, the parasites are also sent packing.

Prometheus, who has always despised Zeus, covers his head and sneaks off to see Pisthetaerus. He reports the gods won’t hold out much longer and will soon be coming to make peace. Sure enough, the gods’ messengers Poseidon, Heracles and Triballus arrive in cloud cuckoo land. Pisthetaerus demands Zeus relinquish his rule and he give him Basileia, who controls Zeus’ thunderbolts, in marriage. The gods are forced to submit to the demands. A cheerful wedding is held in the woods. Pisthetaerus becomes king of Nubicuculia, and spends his days happily labouring and living among the birds.