The imperial shag is a black and whitecormorant native to southern South America, primarily in rocky coastal regions, but locally also at large inland lakes. Some taxonomic authorities, including the International Ornithologists' Union, place it in the genusLeucocarbo, others in the genus Phalacrocorax. It is also known as the blue-eyed shag, blue-eyed cormorant and by many other names, and is one of a larger group of cormorants called blue-eyed shags. The taxonomy is very complex, and several former subspecies are often considered separate species.
Taxonomy
The taxonomy is very complex and species-limits within this group remain unresolved. Some taxonomic authorities, including the International Ornithologists' Union, split the group into the species listed below. Others consider the all or part of the group conspecific. The following are considered part of this group:
Imperial shag, Leucocarbo atriceps, from coastal southern Chile and Argentina.
* King cormorant/white-bellied shag, Leucocarbo albiventer, from the Falkland Islands, and locally in southern Argentina and Chile.
, Argentina While some authorities consider all of the above – except albiventer – as separate species, others consider all as subspecies of a single species. Alternatively, some recognize two species, the white-cheeked L. atriceps and the black-cheeked L. albiventer, or it has been suggested that three species should be recognized: L. atriceps, L. georgianus, and L. melanogenis.
Description
The imperial shag has a total length of and weighs, with males usually larger than females. It is endowed with glossy black feathers covering most of its body, with a white belly and neck. It possesses a distinctive ring of blue skin around its eyes, an orange-yellow nasal knob, pinkish legs and feet, and an erectile black crest. During the non-breeding season, adults lack the crest, have a duller facial area, and less/no white to the back/wings. It has a serrated bill used for catching fish. The group varies primarily in the amount of white on the cheeks/ear-coverts, wing-coverts and back. Most taxa have white cheeks and ear-coverts, but these are black in albiventer, purpurascens and melanogenis. Chicks are uniform brownish, and immatures are brownish and white, have dull facial skin, and lack the orange-yellow nasal knob and blue eye-ring.
Behavior
Breeding
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. Up to five eggs are placed in a nest made of seaweed and grass, and cemented together with mud and excrement. The eggs usually hatch in about five weeks, and are brooded by both parents. Many chicks and eggs are lost to predators such as skuas and sheathbills.
Feeding
The diet of this species consists of small benthic fish, crustaceans, polychaetes, gastropods and octopuses. They primarily feed on fish, especially Argentine anchoita,. Mean diving depth is almost,. Most feeding takes place in inshore regions, but at least some populations will travel some distance from the shore to fish.
Status
Overall this species is not considered threatened and is consequently listed as Least Concern by BirdLife International and IUCN. Most subspecies are relatively common with estimates of over 10,000 pairs of each
