I'm assuming this is an Imperial Shag or perhaps a King Cormorant, as the taxonomy of this bird is rather complex with changes being made even in recent years. When I was in South Georgia in 2012, the naturalists referred to it as the Imperial Shag, however on my recent trip to Patagonia I learned that the species in the Falklands (where this image was made) are now being referred to as the King Cormorant. Perhaps it will be different again in a few years.
Imperial Shag / King Cormorant
Imperial Shag - 5D3, 560mm, f/5.6, 1/640s, ISO 200