Blue-eyed cormorant or Macquarie Island shag

Blue-eyed cormorants, also called imperial shags, are large seabirds with distinctive black-and-white plumage. Their breast is white, while the back is black, and much of the cheeks and neck are also white. They have a dark brown bill and pink feet.

Adult birds measure approximately 69–74 cm in length and have a wingspan of around 1.1 meters.

The taxonomic classification of these breeding populations remains uncertain at present. However, they are likely to eventually be recognized as distinct endemic populations.

Distribution and Abundance

Blue-eyed cormorants establish breeding colonies along the western coast of southern South America. They are also found breeding on South Georgia, the South Sandwich Islands, the South Orkney Islands, and the South Shetland Islands, as well as along the Antarctic Peninsula as far south as 68° S.

Additional breeding populations occur on Heard Island, the Iles Kerguelen, and Macquarie Island.

During the 2000/01 breeding season, researchers discovered a substantial colony on Heard Island containing approximately 1,000 breeding pairs. Before this discovery, the island's breeding population had been estimated at only 100–200 pairs distributed among three separate colonies.

These cormorants are social birds throughout the entire year. They can gather in very large groups, particularly during winter, when thousands of individuals may congregate offshore in dense rafts on the sea.

Breeding

Courtship begins from late August through early October. Females generally lay two to three eggs between October and early January.

The eggs hatch from November through February. Young birds begin to fledge between January and March, while adult birds leave their breeding colonies during April.

Diet and Feeding

Blue-eyed cormorants primarily consume fish and various invertebrates. They usually hunt underwater at depths of around 25 meters, although some individuals are capable of making much deeper dives reaching approximately 100 meters.

These birds face predation both at their breeding sites and while at sea. Sheathbills, which are opportunistic scavengers and predators, may take blue-eyed cormorant eggs. At sea, leopard seals are known to attack the birds.