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.
♦ ²Energy flow of a boreal intertidal ecosystem, the Sylt-Rømø Bight, Dan Baird, Harald Asmus, Ragnhild Asmus, Mar Ecol Prog Ser 279: 45–61, 2004