The Audubon Park Zoo Birdhouse is designed to be a buffer between the Zoo and the calmness of the birdhouse exhibit. Passive Transport II, made of cast stone, sky blue beveled glass, and pounded lead banding, shows symbols of man and nature, representing a union between earth and sky. Elizabeth Shannon's sculpture, with its strong columnar form and fragile glass insert, reminds us of the contrasting and opposing forces in nature.