Unwelcomed Visitors Motif
Aristophanes has three arrivals of unwelcome visitors that become a motif in the play. The first are the messengers, the second the men seeking the new gods to give them wings and the third the gods themselves sent to negotiate for Zeus.
Wings
The characters are given wings and a head crown of a bird, but they don't fully transform into birds. This is a symbol of the fact that no man can fully leave himself behind to start a new life.
The Princess
The Princess is Zeus' love, and said to be his greatest power. She is a symbol of Zeus' sovereignty over the earth that he gives up.
Scepter
Zeus has a lightning bolt for a scepter that Peisetaerus eventually takes. This scepter is a symbol of Zeus' ability to bring fear to the people and thus have them bow to him as a god.
Birds
The characters' quest to become birds is a main need in the play. This is a symbol that they seek to fly above the arguing over laws that men currently do in Athens. They seek a higher way of life.