Native of Numidia, and later widespread since ancient times throughout the Roman Empire, the guinea fowl appears only in the Archiepiscopal Chapel. In the arbour of the vestibule it is represented eleven times and stands out against the miraculous golden background. The black plumage is vividly rendered with purple, blue and white tesserae, intended to mimic the small lighter spots that characterise its appearance. The nuances in the breast are rendered with purple tesserae. The horn and wattles are outlined by few orange tesserae, cut in different dimensions and laid to render the rounded and soft shape.