These gulls were conspicuous and abundant throughout our voyage. The nominate race is found in South America and Australia, but those in South Africa are the race L. d. vetula which differs in having a dark eye and a shorter bill. It is sometimes split as a separate species called Cape Gull. Three other subspecies are usually recognized from Antarctica, Indian Ocean Subantarctic islands, and Madagascar (Clements, IOC, Jiguet). However the latest Howard & Moore consider the species to be monotypic. New Zealand populations often go under the name "Southern Black-backed Gull" and this was the name used by Howard & Moore through their 2nd edition, but the name Kelp Gull is otherwise universal. A recent publication by Jiguet et al. Zoological Studies 51(6): 881-892 (2012) recommends separation of the Australia/New Zealand population as a distinct subspecies (L. d. antipodus). This suggestion has been adopted by HBW (online version). Canon PowerShot SX50 HS.
References:
Burger, J., Gochfeld, M. & Garcia, E.F.J. (2017). Kelp Gull (Larus dominicanus). 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 http://www.hbw.com/node/53975 on 2 March 2017).
Higgins, P.J.; Davies, S.J.J.F. (Eds.) 1996. Handbook of Australian, New Zealand and Antarctic birds. Vol. 3. Snipe to Pigeons. Oxford University Press: Melbourne
Jiguet, F. (2002) Taxonomy of the Kelp Gull Larus dominicanus Lichtenstein inferred from biometrics and wing plumage pattern, including two previously undescribed subspecies. Bull. Brit. Orn. Club 122(1): 50–71.
http://www.biodiversitylibrary.org/page/40416417#page/74/mode/1up
Jiguet, F., Capainolo, P. & Tennyson, A.J.D. (2012) Taxonomy of the Kelp Gull Larus dominicanus Lichtenstein revisited with sex-separated analyses of biometrics and wing tip patterns. Zool. Stud. 51(6): 881–892.
http://zoolstud.sinica.edu.tw/Journals/51.6/881.pdf
Miskelly, C.M. 2013. Southern black-backed gull. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
Shirihai, H. (2007) A Complete Guide to Antarctic Wildlife. The Birds and Marine Mammals of the Antarctic Continent and the Southern Ocean. 2nd edition. A&C Black, London.