Distribution map of Sterna bergii based on Birds of the Western Palaeartic and Terns of Europe and North America
SternaBergiMap.svg based on Higgins, P. J.; Davies,  S. J. J. F. (eds) (1996)       Handbook of Australian, New Zealand and Antarctic Birds: Volume 3: Snipe to Pigeons, Oxford University Press, Melbourne  ISBN:  0-19-553070-5.   and Olsen, Klaus Malling; Larsson, Hans (1995)       Terns of Europe and North America, London: Christopher Helm  ISBN:  0-7136-4056-1.
derivative work: Jimfbleak (talk)
SternaBergiMap.svg: L Shyamal