Often called the Subantarctic Brown Skua, this race (S. a. lonnbergi) is larger, darker and less heavily marked than Falkland Island birds. This is an adult (top) showing pale forehead blaze. Juveniles such as this (bottom) lack pale streaking and appear uniformly dark. Note fresh feathering with no evidence of molt, lack of wear and no pale blaze on the forehead. Bill is marginally smaller than adult. Taxonomy is complex but Clements, SACC, IOC, HBW, and H&M all recognize three races, each in a different group. In the past, the large skuas were placed in the genus Catharacta and HBW still uses that older classification. Canon PowerShot SX50 HS.
References:
Furness, R.W. (2017). Brown Skua (Catharacta antarctica). 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/53956 on 24 February 2017).
Hemmings, A.D. 2013. Subantarctic skua. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
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
Olsen, K. M. and Larsson, H. 1997. Skuas and Jaegers. Yale Univ. Press.
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.