Cormoran de Magellan

Identification

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.

Taxonomie

The rock shag was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it in the genus Pelecanus and coined the binomial name Pelecanus magellanicus. Gmelin based his description on the "Magellanic shag" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds. Latham had in turn based his description on a specimen in the Leverian Museum and the account made by Georg Forster of his visit to Tierra del Fuego in December 1774 during James Cook's second voyage to the Pacific. The rock shag was formerly placed in the genus Phalacrocorax but based on the results of a molecular genetic study of the cormorants published in 2014, the species was moved to the genus Leucocarbo. The genus had been introduced in 1856 by the French naturalist Charles Lucien Bonaparte. The genus name combines the Ancient Greek leukos meaning "white" with the name Carbo introduced by Bernard Germain de Lacépède in 1799. The species is monotypic: no subspecies are recognised.

Nom scientifique

Leucocarbo magellanicus

Autorité

(Gmelin, JF, 1789)

Ordre

Suliformes

Famille

Phalacrocoracidés

Genre

Leucocarbo

Répartition et habitat

Aire de reproduction

SA : coastal sc Chile and sc Argentina to Cape Horn and Falkland Is.

Aire hors reproduction

to coastal s Brazil

Migration

Complete migrants

Comportement

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, Patagonotothen species) sheltering among the weed. Studies with depth gauges suggest that it is a fairly shallow diver, typically going about 5 m below the surface with few individuals diving deeper than 10 m, although its prey mainly comes 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.<p>The rock shag usually nests on ledges on steep, bare, rocky cliffs. It normally lays three eggs, though nests of from two to five eggs have been seen. Nesting colonies range is size from five pairs to nearly 400.

Conservation

Tendance de la population

unknown