Kerguelen Shag
Encyclopedia
The Kerguelen Shag is a species of cormorant
endemic
to the Kerguelen Islands
. Many authorities consider it a subspecies of the Imperial Shag
.
on the coast of Grande Terre (the main island of the archipelago), on offshore islands, and on islands in the Golfe du Morbihan
. It forages at sea throughout the archipelago, usually within 6 km (3.7 mi) of shore and especially in bays and inlets, though immatures have rarely been seen as far as 80 km (49.7 mi). Reports from Heard Island and western Australia
may be of ship-assisted birds.
In the austral summer it feeds among kelp
, sometimes at the bottom.
. The adult's upperparts, tail, and thighs are metallic greenish black; the underbody to the throat is white; and the wing linings are brown. Some individuals have white patches on the back and wings. The head and the back of the neck are deep blue or purple, except that a black cap reaches below the eye to the chin and ear coverts. The face and throat pouch are dark brown, ornamented with yellow-orange tubercles. The bill is horn-colored or brown; the eyes are hazel. The legs and feet vary from dark brown to dark-blotched bright pink. Breeding adults have a little black erectile crest on the forehead, yellow or orange caruncles (large warts) above the base of the bill, and a bright blue ring around the eye. After the breeding season, the plumage fades, the eye-ring becomes lead-blue, and the caruncles become smaller and duller-colored.
Juveniles are dark brown with varying amounts of white underneath and brown iris, bill, and feet. They have no caruncles, and their eye-rings are lead-blue. They acquire adult plumage gradually.
Unlike many cormorants, this species does not spread its wings when it is perched.
s, crustacean
s, and polychaete
worms. In summer they mostly forage alone, but from May to October they form linear flocks of several hundred, diving and surfacing sequentially down the line.
s. There is a period of nest-building and displaying in late March and early April—an unusual time for a subantarctic cormorant. Advertising males display by throwing the head back till the nape touches the tail. Nests are cones of seaweed, twigs, and grass held together with mud and guano, up to 1 meter tall and 33 cm across, with a cup averaging 20 cm across and 8 cm deep. Nests that survive may be reused, perhaps not by the same pair. Breeding activity starts as early as September, but laying usually starts at some point from late October to late November and lasts till mid January; the times vary considerably among colonies. The clutch comprises 2 to 4 eggs, about 6.2 cm long and 3.9 cm wide. The second egg is laid 2 or 3 days after the first. Both parents incubate for an average of 29 days. Both protect the chicks from predation by skua
s, gull
s, and sheathbill
s, which nevertheless take some chicks. Chicks hatch black with a pink throat and develop blackish-brown down with grayish-white tufts. Other aspects of reproductive behavior and success are unknown.
The population was about 6,000 to 7,000 pairs in 1984–1987. Interactions with human beings and introduced mammals do not appear to be damaging the population.
. Here it is considered a separate species following the Handbook of the Birds of the World
and other authorities
It has been suggested that Heard Shag
s may visit the Kerguelens and that Kerguelen Shags with white wing or back patches are the result of hybridization.
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 :...
endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to the Kerguelen Islands
Kerguelen Islands
The Kerguelen Islands , also known as the Desolation Islands, are a group of islands in the southern Indian Ocean constituting the emerged part of the otherwise submerged Kerguelen Plateau. The islands, along with Adélie Land, the Crozet Islands and the Amsterdam and Saint Paul Islands are part of...
. Many authorities consider it a subspecies 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...
.
Range and habitat
This species nestsBird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
on the coast of Grande Terre (the main island of the archipelago), on offshore islands, and on islands in the Golfe du Morbihan
Golfe du Morbihan (Kerguelen)
The Golfe du Morbihan of the Kerguelen islands forms deep and broad notch in the central section of principal island of the Kerguelen Islands, Grande Terre....
. It forages at sea throughout the archipelago, usually within 6 km (3.7 mi) of shore and especially in bays and inlets, though immatures have rarely been seen as far as 80 km (49.7 mi). Reports from Heard Island and western Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
may be of ship-assisted birds.
In the austral summer it feeds among kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
, sometimes at the bottom.
Description
The Kerguelen Shag is 65 cm (26 in) long with a wingspan of 110 cm (43 in), making it the smallest blue-eyed shagBlue-eyed shag
The blue-eyed shags are a group of closely related cormorant taxa. All have a blue, purple or red ring around the eye ; other shared features are white underparts and pink feet....
. The adult's upperparts, tail, and thighs are metallic greenish black; the underbody to the throat is white; and the wing linings are brown. Some individuals have white patches on the back and wings. The head and the back of the neck are deep blue or purple, except that a black cap reaches below the eye to the chin and ear coverts. The face and throat pouch are dark brown, ornamented with yellow-orange tubercles. The bill is horn-colored or brown; the eyes are hazel. The legs and feet vary from dark brown to dark-blotched bright pink. Breeding adults have a little black erectile crest on the forehead, yellow or orange caruncles (large warts) above the base of the bill, and a bright blue ring around the eye. After the breeding season, the plumage fades, the eye-ring becomes lead-blue, and the caruncles become smaller and duller-colored.
Juveniles are dark brown with varying amounts of white underneath and brown iris, bill, and feet. They have no caruncles, and their eye-rings are lead-blue. They acquire adult plumage gradually.
Unlike many cormorants, this species does not spread its wings when it is perched.
Feeding
Kerguelen Shags presumably eat mostly fish and such invertebrates as echinodermEchinoderm
Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....
s, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, and polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
worms. In summer they mostly forage alone, but from May to October they form linear flocks of several hundred, diving and surfacing sequentially down the line.
Reproduction
This species breeds in colonies, usually of 3 to 30 pairs but occasionally up to 400. Colonies may be near those of Rockhopper PenguinRockhopper penguin
The rockhopper penguins are three closely related taxa of crested penguins that have been traditionally treated as a single species and are sometimes split into two or three species. Not all experts agree on the classification of these penguins...
s. There is a period of nest-building and displaying in late March and early April—an unusual time for a subantarctic cormorant. Advertising males display by throwing the head back till the nape touches the tail. Nests are cones of seaweed, twigs, and grass held together with mud and guano, up to 1 meter tall and 33 cm across, with a cup averaging 20 cm across and 8 cm deep. Nests that survive may be reused, perhaps not by the same pair. Breeding activity starts as early as September, but laying usually starts at some point from late October to late November and lasts till mid January; the times vary considerably among colonies. The clutch comprises 2 to 4 eggs, about 6.2 cm long and 3.9 cm wide. The second egg is laid 2 or 3 days after the first. Both parents incubate for an average of 29 days. Both protect the chicks from predation by skua
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....
s, gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s, and sheathbill
Sheathbill
The sheathbills are a family of birds, Chionidae. Classified in the wader order Charadriiformes, the family contains one genus, Chionis, with only two species...
s, which nevertheless take some chicks. Chicks hatch black with a pink throat and develop blackish-brown down with grayish-white tufts. Other aspects of reproductive behavior and success are unknown.
The population was about 6,000 to 7,000 pairs in 1984–1987. Interactions with human beings and introduced mammals do not appear to be damaging the population.
Classification
This species has been placed in genera Halieus, Hypoleucos, Notocarbo, and Leucocarbo. It is often considered conspecific with some other blue-eyed shags under the name Imperial ShagImperial 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...
. Here it is considered a separate species following the Handbook of the Birds of the World
Handbook of the Birds of the World
The Handbook of the Birds of the World is a multi-volume series produced by the Spanish publishing house Lynx Edicions. It is the first handbook to cover every known living species of bird. The series is edited by Josep del Hoyo, Andrew Elliott, Jordi Sargatal and David A Christie.So far, 15...
and other authorities
It has been suggested that Heard Shag
Heard Shag
The Heard Island Shag , or Heard Island Cormorant, is a marine cormorant native to the Australian territory comprising the Heard and McDonald Islands in the Southern Ocean, about 4100 km south-west of Perth, Western Australia.-Taxonomy:The Heard Island Shag is one of the blue-eyed shags,...
s may visit the Kerguelens and that Kerguelen Shags with white wing or back patches are the result of hybridization.