Plumage aberrations are common, particularly in waterfowl. There have been numerous proposed causes including the retention of ancestral plumage characters that contain phylogenetic information. A partial white neck ring was observed in Yellow-billed Pintail Anas georgica spinicauda near Cusco, Peru. Non-typical white neck rings have been reported in other waterfowl species. Although the exact cause is unclear, its reoccurrence in other species and the consistent placement suggest that this unusual plumage could be of evolutional significance. ©Wildfowl & Wetlands Trust.