This New Caledonian endemic subspecies is larger than the nominate race found in Australia and it has a different wing pattern. Some authors claim that C. n. forsteri also occurs in Northern and Northeastern Australia, but that is incorrect.. Formerly included in the genus Larus, these medium/small gulls were common at Kuto Bay. Three subspecies are recognized. The Red-billed Gull of New Zealand is now included in this species. Red-billed differs in having a shorter, stubbier, more arched bill and a more squared pattern of white in its wing-tips when seen in flight. Canon PowerShot SX60.
References:
Burger, J., Gochfeld, M., Kirwan, G.M. & Garcia, E.F.J. (2019). Silver Gull (Larus novaehollandiae). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53991 on 11 December 2019).
Dutson, G. (2011) Birds of Melanesia, Christopher Helm, London.
Higgins, P.J. & Davies, S.J.J.F. (editors) 1996. Handbook of Australian , New Zealand & Antarctic Birds. Volume 3, Snipe to pigeons. Melbourne, Oxford University Press.
Mills, J.A. 2013. Red-billed gull. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz