Imperial Shag - Taxonomy

Taxonomy

The taxonomy is very complex and species-limits within this group remain unresolved. The following are usually considered part of this group:

• Imperial Shag, Phalacrocorax (atriceps) atriceps, from coastal southern Chile and Argentina.
• King Cormorant/White-bellied Shag, Phalacrocorax (atriceps) albiventer, from the Falkland Islands, and locally in southern Argentina and Chile.
• Antarctic Shag, Phalacrocorax (atriceps) bransfieldensis, from the Antarctic Peninsula and the South Shetland Islands.
• South Georgia Shag, Phalacrocorax (atriceps) georgianus, from the South Georgia and the South Sandwich Islands, and South Orkney Islands.
• Heard Shag, Phalacrocorax (atriceps) nivalis, from Heard Island.
• Crozet Shag, Phalacrocorax (atriceps) melanogenis, from the Crozet and Prince Edward Islands.
• Macquarie Shag, Phalacrocorax (atriceps) purpurascens, from Macquarie Island.

While some authorities accept all of the above – except albiventer – as separate species, others consider all as subspecies of a single species (as done in this article). Alternatively, some recognize two species, the white-cheeked P. atriceps (with subspecies bransfieldensis, nivalis and georgianus) and the black-cheeked P. albiventer (with subspecies melanogenis and purpurascens), or it has been suggested that three species should be recognized: P. atriceps (incl. albiventer), P. georgianus (with subspecies bransfieldensis and nivalis), and P. melanogenis (with subspecies purpurascens and possibly verrucosus, though the latter is relatively distinctive, and most consider it a separate species, the Kerguelen Shag).