It is also known as the blue-eyed shag, blue-eyed cormorant, king cormorant and by many other names.
This is a colonial, monogamous species. The colonies are usually relatively small, but some consist of hundreds of pairs and are often shared with other seabirds such as rock shags, southern rockhopper penguins and black-browed albatrosses.
When flying back to the nest, somehow they know which ones are theirs! After many hours watching them I had not seen one misidentified its nest and mate!