Based on the ancient belief that the peacock's flesh does not decay - Saint Augustine details a rather odd account of discovering the peacock's "antiseptic qualities" and reputed incorruptibility - the bird acquired an association in Christian art with Christ's Resurrection. An additional belief that the bird loses its feathers in autumn and re-grows them in the spring augmented its value as a symbol of the Resurrection.
Images of the peacock adorn all manner of Christian art, from catacomb painting to mosaic church decoration to liturgical objects, and the bird appears occasionally in scenes of Christ's Nativity. Take for example the image above, a detail of The Adoration of the Magi by Fra Angelico and Fra Filippo Lippi, housed at the National Gallery of Art in Washington, D.C. A peacock perched atop the stable where Christ has been born calls to mind His Resurrection, through which Christ opens for us the way to life everlasting.
Curator of Art
Sources: Saint Augustine of Hippo, City of God, Book XXI, Ch 4; Impelluso, Lucia, Nature and Its Symbols, Los Angeles: Getty Museum, 2003; Hall, James, Dictionary of Subjects and Symbols in Art, Boulder, CO: Westview Press, 1974.