Distribution map of Sterna bergii based on 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. and Olsen, Klaus Malling; Larsson, Hans (1995). Terns of Europe and North America. London: Christopher Helm.
Own work
L Shyamal