From Opus

Includes King Cormorant, Heard Island Shag, and Macquarie Shag; Alternative Names: Blue-eyed Shag.

Dark-cheeked form
Photo by Sussex bird man
Photo taken: Beagle Straits, Ushuaia, Argentina, November 2005

Phalacrocorax atriceps

[edit] Identification

Black feathers upper parts, white belly and neck. Ring of blue skin around its eyes and a bright orange nasal tuft and black crest above eyes, all of which is missing in immature birds which are browner than adults.

Two main variations: dark-cheeked forms dominate on the Atlantic side while white-cheeked forms dominate on the Pacific side of South America. These forms meet and hybridize (to some extent) in the Patagonia/Magellan Strait region.

[edit] Distribution

Seacoasts of extreme southern South America and sub-Antarctic islands: Falkland Islands, Heard Island and Macquarie Island.

White-cheeked form
Photo by Rodrigo Reyes
Photo taken: Puerto Montt, southern Chile, February 2009

[edit] Taxonomy

[edit] Subspecies¹

• P. a. atriceps - Islands and coasts of s Argentina and Chile
• P. a. albiventer - Falkland Islands
• P. a. nivalis - "Heard Island Shag"; Heard Island
• P. a. purpurascens - "Macquarie Shag"; Macquarie I. and adjacent Bishop and Clerk Rocks

[edit] Status of questionable forms

South Georgia Shag and Antarctic Shag have recently been split from Imperial Shag by a majority of authorities, but at this time, not everybody agrees.
Some authorities (Clements, 2007) treat P. a. nivalis (Heard Island Shag) and P. a. purpurascens (Macquarie Shag) as full species. However, Howard & Moore (2003) and Sibley & Monroe (1996) keep them lumped within P. atriceps and the Opus awaits further clarification.

Dark-cheeked birds from southern South America have in the past been known as the full species King Shag (Phalacrocorax albiventer) together with birds from the Falklands. Due to reports on hybridization with atriceps these were first lumped as a subspecies under Imperial Shag, and later, the mainland birds were considered a color morph of atriceps leaving the population on Falklands as the current subspecies albiventer. Not everybody agree that the current treatment of the dark-cheeked form is the best possible treatment^[3], but more data are necessary.

[edit] Habitat

Rocky sea coasts.

[edit] Behaviour

The diet of this species is mainly fish. It can dive to a depth of almost 25m and eats mainly Argentine anchoita.

[edit] References

1. Clements, James F. 2007. The Clements Checklist of Birds of the World. 6th ed., with updates to October 2007. Ithaca: Cornell University Press. ISBN 9780801445019
2. Alvaro Jaramillo. 2003. Birds of Chile. Princeton Field Guides. ISBN 0-691-11740-3
3. Thread in the taxonomy forum discussing the different splits and lumps in the species mentioned here.

[edit] External Links