Alternative Names: Blue-eyed Shag; Imperial Shag
- Leucocarbo atriceps
Phalacrocorax atriceps
Includes King Cormorant
Identification
Length: 68–76 cm (26¾-30 in)
Black upper parts contrast with white belly and foreneck. Black crest, blue orbital skin and bright yellow nasal caruncles are missing in nonbreeding birds which have a reduced white wing patch. Immatures are similar to nonbreeding adults but browner.
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.
Distribution
Seacoasts of extreme southern South America and sub-Antarctic islands: Falkland Islands, Heard Island and Macquarie Island.
Taxonomy
Sometimes placed in the genus Phalacrocorax.
Subspecies
This is a polytypic species[1]. Two subspecies recognized.
- L. a. atriceps - Islands and coasts of s Argentina and Chile
- L. a. albiventer - Falkland Islands
Photo © by Peter Cranstall
Sealion island, Falkland Islands, 30 June 2013
Status of questionable forms
South Georgia Shag, Heard Island Shag, Crozet Shag, Macquarie Shag and Antarctic Shag have recently been split from Imperial Shag by a majority of authorities, but at this time, not everybody agrees.
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.
Habitat
Rocky sea coasts.
Behaviour
Actions
Male advertisement display consists of a head throwback with the bill open and an aark call while the tail is raised. Mated birds communicate by gaping, head lowering, and throat clicking.
Breeding
Breeds in small colonies on coastal areas and low islands. Nesting materials include marine algae, feathers, sticks and shells and cemented guano. Clutch size usually 3 chalky-blue eggs but last egg often discarded.
Diet
Primarily fish such as Argentine anchoita, but they also eat crustaceans, cephalopods and polychaetes. They are bottom feeders and dive to a depth of almost 25 meters.
Movements
Usually resident but disperses from breeding colonies depending on food availability.
Vocalisations
Males and females have different calls. During breeding, male gives barking “aark” and various other honking calls while females have a hissing call.
References
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2018. The eBird/Clements checklist of birds of the world: v2018. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
- Jaramillo, A. 2003. Birds of Chile. Princeton & Oxford: Princeton Univ. Press. ISBN 978-0691117409
- Thread in the taxonomy forum discussing the different splits and lumps in the species mentioned here.
- Gómez Laich, A. (2012). Imperial Cormorant (Phalacrocorax atriceps), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.impcor1.01
- Orta, J., Garcia, E.F.J., Christie, D.A., Jutglar, F. & Kirwan, G.M. (2019). Imperial Shag (Leucocarbo atriceps). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52649 on 24 January 2019).
- Davis, M. 2017. "Phalacrocorax atriceps" (On-line), Animal Diversity Web. Accessed January 24, 2019 at https://animaldiversity.org/accounts/Phalacrocorax_atriceps/
Recommended Citation
- BirdForum Opus contributors. (2024) Imperial Cormorant. In: BirdForum, the forum for wild birds and birding. Retrieved 1 June 2024 from https://www.birdforum.net/opus/Imperial_Cormorant
External Links
GSearch checked for 2020 platform.1
