Rock Shag
Encyclopedia
The Rock Shag also known as the Magellanic cormorant, is a marine cormorant
found around the southernmost coasts of South America
. Its breeding range is from around Valdivia
, Chile
, south to Cape Horn
and Tierra del Fuego
, and north to Punta Tombo
in Argentina
. In winter it is seen further north, with individuals reaching as far as Santiago, Chile
on the west coast and Uruguay
on the east. The birds also breed around the coasts of the Falkland Islands
At a distance, the Rock Shag is a black and white bird, with head, neck and upperparts black and chest and underparts white. Closer up, the black areas vary from metallic blue to oily green, and are flecked with white in places. The legs and feet are a pink, fleshy colour, and the bare flesh around the beak and eyes is brick red. In breeding condition, there is a blackish though not very prominent crest on the forehead, and a distinctive white ear patch. There is even less sexual dimorphism
than in most cormorant species, but males are 5%-10% larger on most size measurements.
Like all cormorants, the Rock Shag feeds by diving for underwater prey. It feeds close to shore, often diving at the edge of kelp
beds and apparently finding small fish (predominantly cod icefishes, Patagonothen sp.) sheltering among the weed. Studies with depth gauge
s suggest that it is a fairly shallow diver, typically going about 5m below the surface with few individuals ever diving deeper than 10m, although its prey mainly come from the sea floor. Dive times are typically around 30 seconds. Its breeding range overlaps markedly with that of the Imperial Shag
Leucocarbo atriceps, but the two species' foraging ranges are different since the Imperial Shag tends to dive in deeper water, further out from shore.
The Rock Shag usually nests on ledges on steep, bare, rocky cliffs. It normally lays 3 eggs, though nests of from 2 to 5 eggs have been seen. Nesting colonies range is size from 5 pairs to nearly 400.
Like a number of other species of cormorant that are commonly called shags, the Rock Shag is placed by some authors in a genus Leucocarbo. Cladistic analysis suggests that it is related to other cliff-nesting species such as the Red-footed Shag, Pelagic cormorant
and Red-faced Shag.
Cormorant
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
found around the southernmost coasts of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. Its breeding range is from around Valdivia
Valdivia, Chile
Valdivia is a city and commune in southern Chile administered by the Municipality of Valdivia. The city is named after its founder Pedro de Valdivia and is located at the confluence of the Calle-Calle, Valdivia and Cau-Cau Rivers, approximately east of the coastal towns of Corral and Niebla...
, Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, south to Cape Horn
Cape Horn
Cape Horn is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island...
and Tierra del Fuego
Tierra del Fuego
Tierra del Fuego is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of a main island Isla Grande de Tierra del Fuego divided between Chile and Argentina with an area of , and a group of smaller islands including Cape...
, and north to Punta Tombo
Punta Tombo
Punta Tombo is a peninsula into the Atlantic Ocean south of Trelew in Chubut Province, Argentina, where there is an important colony of Magellanic Penguins...
in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. In winter it is seen further north, with individuals reaching as far as Santiago, Chile
Santiago, Chile
Santiago , also known as Santiago de Chile, is the capital and largest city of Chile, and the center of its largest conurbation . It is located in the country's central valley, at an elevation of above mean sea level...
on the west coast and Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
on the east. The birds also breed around the coasts of the Falkland Islands
Falkland Islands
The Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...
At a distance, the Rock Shag is a black and white bird, with head, neck and upperparts black and chest and underparts white. Closer up, the black areas vary from metallic blue to oily green, and are flecked with white in places. The legs and feet are a pink, fleshy colour, and the bare flesh around the beak and eyes is brick red. In breeding condition, there is a blackish though not very prominent crest on the forehead, and a distinctive white ear patch. There is even less sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
than in most cormorant species, but males are 5%-10% larger on most size measurements.
Like all cormorants, the Rock Shag feeds by diving for underwater prey. It feeds close to shore, often diving at the edge of kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
beds and apparently finding small fish (predominantly cod icefishes, Patagonothen sp.) sheltering among the weed. Studies with depth gauge
Depth gauge
A depth gauge is a pressure gauge that displays the equivalent depth in water. It is a piece of diving equipment often used by SCUBA divers.Most modern diving depth gauges have an electronic mechanism and digital display. Older types used a mechanical mechanism and analogue display.A diver uses a...
s suggest that it is a fairly shallow diver, typically going about 5m below the surface with few individuals ever diving deeper than 10m, although its prey mainly come from the sea floor. Dive times are typically around 30 seconds. Its breeding range overlaps markedly with that of the Imperial Shag
Imperial Shag
The Imperial Shag, Phalacrocorax atriceps, is a black and white cormorant native to many subantarctic islands, the Antarctic Peninsula and southern South America, primarily in rocky coastal regions, but locally also at large inland lakes. It is sometimes placed in the genus Leucocarbo instead...
Leucocarbo atriceps, but the two species' foraging ranges are different since the Imperial Shag tends to dive in deeper water, further out from shore.
The Rock Shag usually nests on ledges on steep, bare, rocky cliffs. It normally lays 3 eggs, though nests of from 2 to 5 eggs have been seen. Nesting colonies range is size from 5 pairs to nearly 400.
Like a number of other species of cormorant that are commonly called shags, the Rock Shag is placed by some authors in a genus Leucocarbo. Cladistic analysis suggests that it is related to other cliff-nesting species such as the Red-footed Shag, Pelagic cormorant
Pelagic Cormorant
The Pelagic Cormorant , also known as Baird's Cormorant, is a small member of the cormorant family Phalacrocoracidae. Analogous to other smallish cormorants, it is also called Pelagic Shag occasionally...
and Red-faced Shag.