This South Georgia endemic is a member of the Blue-eyed Shag group and is sometimes called South Georgia Blue-eyed Shag. It is similar to the Antarctic Shag (P. bransfieldensis) but Antarctic has more white on its face. The birds with yellow nasal caruncles are post-breeding adults which lack a crest and have a reduced white wing patch. Immatures lack yellow caruncles.
Taxonomy is complex. Here I follow Clements and IOC which split several former subspecies into full species. However other authors (HBW, Howard & Moore 4th) lump the Heard Island, Crozet, Macquarie, South Georgia, and Antarctic Shags as races of Imperial Shag (Phalacrocorax atriceps). SACC is waiting for a formal proposal before splitting Antarctic Shag. Canon PowerShot SX50 HS
References:
Gómez Laich, A. (2012). Imperial Cormorant (Phalacrocorax atriceps), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.impcor1.01
Orta, J., Garcia, E.F.J., Christie, D.A., Jutglar, F. & Kirwan, G.M. (2018). South Georgia Shag (Phalacrocorax georgianus). 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/52651 on 6 June 2018).
Shirihai, H. (2002) A Complete Guide to Antarctic Wildlife. The Birds and Marine Mammals of the Antarctic Continent and the Southern Ocean. Princeton University Press: Princeton & Oxford.