Attributes / relations provided by
♦ ¹del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.
♦ ²Correlates between morphology, diet and foraging mode in the Ladder Snake Rhinechis scalaris (Schinz, 1822), Juan M. Pleguezuelos , Juan R. Fernández-Cardenete , Santiago Honrubia , Mónica Feriche , Carmen Villafranca, Contributions to Zoology, 76 (3) – 2007