Cormorant

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For other uses, see Cormorant (disambiguation).
Cormorants and shags

Little Pied Cormorant
(Phalacrocorax melanoleucos)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Pelecaniformes
Family: Phalacrocoracidae
Reichenbach, 1850
Genus: Phalacrocorax (but see text)
Brisson, 1760
Species

1-8, see text
Synonyms

Australocorax
Compsohalieus
Euleucocarbo
Halietor
Hypoleucos
Leucocarbo
Microcarbo
Miocorax
Nannopterum
Nesocarbo
Notocarbo
Paracorax
Pliocarbo
Stictocarbo
(but see text)

The bird family Phalacrocoracidae is today 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.

Contents

  • 1 Names
  • 2 Characteristics
  • 3 Systematics
    • 3.1 Species in HBW sequence
    • 3.2 Species in phylogenetic sequence
    • 3.3 Evolution and fossil record
  • 4 Cormorant fishing
  • 5 Cultural references
  • 6 References
    • 6.1 Footnotes
  • 7 External links

[edit] Names

There is no consistent distinction between cormorants and shags. The names "cormorant" and "shag" were originally the common names of the two species of the family found in Great Britain, Phalacrocorax carbo (now referred to by ornithologists as the Great Cormorant) and P. aristotelis (the Common Shag). "Shag" refers to the bird's crest, which the British forms of the Great Cormorant lack. As other species were discovered by English-speaking sailors and explorers elsewhere in the world, some were called cormorants and some shags, depending on whether they had crests or not. Sometimes the same species is called a cormorant in one part of the world and a shag in another, e.g., the Great Cormorant is called the Black Shag in New Zealand (the birds found in Australasia have a crest that is absent in European members of the species). Van Tets (1976) proposed to divide the family into two genera and attaching the name "Cormorant" to one and "Shag" to the other, but this flies in the face of common usage and has not been widely adopted.

The scientific genus name is latinized Ancient Greek, from φαλακρός (phalakros, "bald") and κόραξ (korax, "raven"). This is often thought to refer to the creamy white patch on the cheeks of adult Great Cormorants, or the ornamental white head plumes prominent in Mediterranean birds of this species, but is certainly not a unifying characteristic of cormorants. "Cormorant" is a contraction derived from Latin corvus marinus, "sea raven". Indeed, "sea raven" or analogous terms were the usual terms for cormorants in Germanic languages until after the Middle Ages, and the erroneous belief that these birds were related to ravens lasted at least to the 16th century:

"...le bec semblable à celuy d'un cormaran, ou autre corbeau." (..."the beak similar to that of a cormorant or other corvids."; Thevet, 1558).

[edit] Characteristics

Cormorants and shags are medium-to-large seabirds. They range in size from the Pygmy Cormorant (Phalacrocorax pygmaeus), at as little as 45 cm (18 in) and 340 g (12 oz), to the Flightless Cormorant (Phalacrocorax harrisi), at a maximum size 100 cm (40 in) and 5 kg (11 lbs). The recently-extinct Spectacled Cormorant (Phalacrocorax perspicillatus) was rather larger, at an average size of 6.3 kg (14 lbs). The majority, including nearly all Northern Hemisphere species, have mainly dark plumage, but some Southern Hemisphere species are black and white, and a few (e.g. the Spotted Shag of New Zealand) are quite colourful. Many species have areas of coloured skin on the face (the lores and the gular skin) which can be bright blue, orange, red or yellow, typically becoming more brightly coloured in the breeding season. The bill is long, thin, and sharply hooked. Their feet have webbing between all four toes, as in their relatives.

Imperial Shags in Beagle Channel

They are coastal rather than oceanic birds, and some have colonised inland waters - indeed, the original ancestor of cormorants seems to have been a fresh-water bird, judging from the habitat of the most ancient lineage. They range around the world, except for the central Pacific islands.

All are fish-eaters, dining on small eels, fish, and even water snakes. They dive from the surface, though many species make a characteristic half-jump as they dive, presumably to give themselves a more streamlined entry into the water. Under water they propel themselves with their feet. Some cormorant species have been found, using depth gauges, to dive to depths of as much as 45 metres.

After fishing, cormorants go ashore, and are frequently seen holding their wings out in the sun; it is assumed that this is to dry them. Unusually for a water bird, their feathers are not waterproofed. This may help them dive quickly, since their feathers do not retain air bubbles.

Cormorants are colonial nesters, using trees, rocky islets, or cliffs. The eggs are a chalky-blue colour. There is usually one brood a year. The young are fed through regurgitation. They typically have deep, ungainly bills, showing a greater resemblance to those of the pelicans', to which they are related, than is obvious in the adults.

[edit] Systematics

The cormorants are a group traditionally placed within the Pelecaniformes or, in the Sibley-Ahlquist taxonomy, the expanded Ciconiiformes. This latter group is certainly not a natural one, and even after the tropicbirds have been recognized as quite distinct, the remaining Pelecaniformes seem not to be entirely monophyletic. Their relationships and delimitation - apart from being part of a "higher waterfowl" clade which is similar but not identical to Sibley & Ahlquist's "pan-Ciconiiformes" - remain mostly unresolved.

Nonwithstanding, all evidence agrees that the cormorants and shags are closer to the darters and Sulidae (gannets and boobies), and perhaps the pelicans and/or even penguins, than to all other living birds (Kennedy et al. 2000, Mayr 2005). In recent years, three preferred treatments have emerged: either to leave all living cormorants in a single genus, Phalacrocorax, or to split off a few species like the Imperial Shag complex (in Leucocarbo) and perhaps the Flightless Cormorant. Alternatively, the genus may be disassembled altogether and in the most exreme case be reduced to the Great, White-breasted and Temminck's Cormorants. See Siegel-Causey (1988), Orta (1992) and Kennedy et al. (2000) for a review of classification schemes.

Pending a thorough review of the Recent and prehistoric cormorants, the single-genus approach of Orta (1992) is followed here for three reasons: First, it is preferrable to tentatively assigning genera without a robust hypothesis. Second, it makes it easier to deal with the fossil forms, the systematic treatment of which has been no less controversial than that of living cormorants and shags. Third, this scheme is also used by the IUCN (2006), making it easier to incorporate status data. In accordance with the treatment there, the Imperial Shag complex is here left unsplit too, but the King Shag complex ist split up.

Several evolutionary groups are still recognizable. However, combining the available evidence suggests that there has also been a great deal of convergent evolution; for example the "cliff shags" are a convergent paraphyletic group. The proposed division into Phalacrocorax sensu stricto (or subfamily Phalacrocoracinae) "cormorants" and Leucocarbo sensu lato (or Leucocarboninae) "shags" (van Tets 1976, Siegel-Causey 1988) does indeed have some degree of merit - though not as originally intended -, but fails to account for basal linages and the fact that the entire family cannot be clearly divided at present beyond superspecies or species complex level (Kennedy et al. 2000). The resolution provided by the mtDNA 12S rRNA and ATPase subunits 6 and 8 sequence data of Kennedy et al. (2000) is not sufficient to properly resolve several groups to satisfaction; in addition, many species remain unsampled, the fossil record has not been integrated in the data, and the effects of hybridization - known in some Pacific species especially - on the DNA sequence data are unstudied.

[edit] Species in HBW sequence

This sequence follows Orta (1992)

[edit] Species in phylogenetic sequence

This list attempts to follow a phylogenetic order based on Orta (1992) and Kennedy et al. (2000). If the distinction into subfamilies would be upheld, the "blue-eyed" and related species would probably be the Leucocarboninae, and the groups that follow hem the Phalacrocoracinae. The first two lineages (and possibly the Flightless Cormorant) are basal and cannot be assigned to either subfamily.

Little Cormorant, Phalacrocorax niger

Basal lineage 1: "Microcormorants", proposed genus Microcarbo or Halietor ("Phalacrocoracinae"); the former genus name would be valid.

Small, short-billed subtropical to tropical marine and freshwater species from the Old World and Australia. They have black feet and almost all lack significant white feathers. Often diminutive frontal tuft.

Basal lineage 2: Red-footed Shag. Included in Leucocarbo or Stictocarbo ("Leucocarboninae")

Pacific coast of South America, apparently no close living relatives. Highly apomorphic color pattern; naked red base of bill, red feet, white neck spot, crestless [1]. Apparently convergent in some aspects with punctatus superspecies.[1]
The Double-crested Cormorant's crests are normally not visible

Blue-eyed shags and relatives: variously placed in Euleucocarbo, Hypoleucos Leucocarbo, Notocarbo and Stictocarbo ("Leucocarboninae")

This reasonably well-supported marine clade contains 3 lineages:
  1. One containing American species which are black-footed, black-plumaged, and have vellow skin at the base of the bill as well as rather inconspicuous crests. They occur in marine and freshwater habitats
  2. The Rock Shag from southern South America with red skin at the bill base, pink feet, a frontal crest, and an apomorphic white ear-spot
  3. A group of numerous close-knit forms from southern Pacific and subantarctic waters which are white below with pink feet but otherwise quite varying in appearance. Contains the King and Imperial complexes and the Guanay Cormorant. Almost all have some amount of white on the upperwing coverts, frontal crests, and blue eye-rings. The crested shags with yellow warts in front of the eyes belong into this group. The genus name Leucocarbo would apply to either this group, or the entire clade.
Guanay Cormorant, Phalacrocorax bougainvillii
Brandt's Cormorant (Phalacrocorax penicillatus) - crestless, but with ornamental plumes

North Pacific shags: spread between Compsohalieus ("Phalacrocoracinae") and Stictocarbo ("Leucocarboninae"). If a distinct genus, the former name would apply

A well-supported marine group ranging from the Bering Strait to California. Black-footed and with white ornamental plumes strewn about the head and neck in breeding plumage. Tend to have prominent double crests.

Common Shag lineage: formerly in Compsohalieus ("Phalacrocoracinae") and Stictocarbo ("Leucocarboninae")

Black-footed smallish marine shags of Europe and southern Africa. Wahlberg's Cormorant is very tentatively placed here, it seems anatomically more similar to the P. fuscscens, but the more informative characters - the combination of frontal crest and lack of extensive naked skin at bill base in mid-sized Old World species - seem to place it here. If this is correct, they are probably very distantly related due to biogeography.

Indian Ocean group: spread between Hypoleucos and Leucocarbo ("Leucocarboninae") and Compsohalieus ("Phalacrocoracinae"). Hypoleucos would be the correct genus name if they were split off.

Little Black Cormorant, Phalacrocorax sulcirostris
A group of black-footed species occurring in tropical coastal or inland habitat between the Persian Gulf and Australia. Most species are tentatively assigned here, based on the combination of range, crestlessness, size, general lack of naked skin ornaments and the presence of some amount of white feathering in the ear region at least in breeding plumage. This clade is not too well-supported, but this may be because the two presumed members studied by Kennedy et al. (2000) are quite dissimilar; the three unstudied ones are are very similar to one or the other.

Spotted group: placed in Stictocarbo ("Leucocarboninae"); indeed, they would be the only members of this possibly distinct genus

A superspecies of the New Zealand region. Peculiarly apomorphic, with yellowish legs, prominent double crests, white ornamental plumes on the neck, a grey belly and spotted wings.

Cape Cormorant: sometimes placed in Leucocarbo ("Leucocarboninae")

Highly plesiomorphic among its relatives; a species from the southern coasts of Africa. It is apparently close to the common ancestor of the next group and, perhaps apart form the all-black plumage, looks probably almost identical to that long-extinct bird.
Great Cormorant (Phalacrocorax carbo) drying its wings

True cormorants: these would be retained in Phalacrocorax no matter how the cormorants and shags are split up

Occurring from the western Atlantic through the Old World into Australia, usually but not always in marine and temperate to subtropical habitat. They are characteristic, being large, with white cheek and thigh patches, ornamental plumes in the neck, a yellow naked bill base, black feet, and a shaggy nape crest.

Incertae sedis: Occasionally placed in the monotypic genus Nannopterum, alternatively Compsohalieus ("Phalacrocoracinae") or Leucocarbo ("Leucocarboninae")

The relationships of this species remain unresolved. Confined to the Galapagos Islands, its wings have evolved to the size of a penguin's flippers. It is extremely apomorphic due to its flightlessness, and its plumage is entirely nondescript. It might be a derivative of the North Pacific lineage, or even the only cormorant somewhat closer to the Red-footed Shag.

[edit] Evolution and fossil record

Little can be said about the original origins of living cormorants. Not even biogeography, usually very informative, provides conclusive data for this probably rather ancient and widespread group. While the leucocarbonines are almost certainly of southern Pacific origin - possibly even Antarctic, which at the time when cormorants evolved was not yet ice-covered -, all that can be said about the phalacrocoracines is that they are most diverse in the regions bordering the Indian Ocean, but generally occur over a large area.

Similarly, the origin of the family is shrouded in uncertainties. Some Late Cretaceous fossils have been proposed to belong into the Phalacrocoracidae:
A scapula from the Campanian-Maastrichtian boundary, about 70 mya, was found in the Nemegt Formation in Mongolia; it is now in the PIN collection (Kurochkin 1995). It is from a bird roughly the size of a Spectacled Cormorant, and quite similar to the correesponding bone in Phalacrocorax. A Maastrichtian (Late Cretaceous, c.66 mya) right femur, AMNH 25272 from the Lance Formation near Lance Creek, Wyoming, is sometimes suggested to be the second-oldest record of the Phalacrocoracidae; this was from a rather smaller bird, about the size of a Long-tailed Cormorant (Hope 2002).

As the Early Oligocene "Sula" ronzoni cannot be assigned to any of the suloid families - cormorants and shags, darters, and gannets and boobies - with certainty, the best interpretation is that the Phalacrocoracidae diverged from their closest ancestors in the Early Oligocene, perhaps some 30 million years ago, and that the Cretaceous fossils represent ancestral suloids, "pelecaniforms" or "higher waterbirds"; at least the last lineage is generally believed to have been already distinct and undergoing evolutionary radiation at the end of the Cretaceous. What can be said with certainty is that AMNH 25272 is from a diving bird that used its feet for underwater locomotion; as this is liable to result in some degree of convergent evolution and the bone is missing undisputable neornithine features, it is not entirely certain that the bone is correctly referred to this group (Hope 2002 and see Hesperornithes).

During the late Paleogene, when the family presumably originated, much of Eurasia was covered by shallow seas, as the Indian Plate finally attached to the mainland. Lacking a detailed study, it may well be that the first "modern" cormorants were small species from East, Southeast or South Asia, possibly living in freshwater habitat, that dispersed due to tectonic events. Such a scenario would account for the present-day distribution of cormorants and shags and is not contradicted by the fossil record; as remarked above, a thorough review of the problem is not yet available.

One distinct genus of prehistoric cormorants is generally accepted today, if Phalacrocorax is used for all living species:

The supposed Late Pliocene/Early Pleistocene "Valenticarbo" is a nomen dubium and given its recent age probably not a separate genus.

Oligocorax appears to be paraphyletic - the European species have been separated in Nectornis, and the North Americna ones are placed in the expanded Phalacrocorax. A Late Oligocene fossil cormoran foot from Enspel (Germany), sometimes placed herein, would then be referrable to Nectornis if it proves not to be too distinct. All these early European species might belong to the basal group of "microcormorants", as they agree with them in size and seem to have inhabited the same habitat: subtropical coastal or inland waters.

The remaining species are, in accordance with the scheme used in this article, all placed in the modern genus Phalacrocorax:

The former "Phalacrocorax" (or "Oligocorax") mediterraneus is now considered to belong to the bathornithid Paracrax antiqua (Cracraft 1971).

[edit] Cormorant fishing

Japanese man displaying ancient cormorant night fishing technique.

Humans have historically exploited cormorants' fishing skills, in China, Japan, and Macedonia, where they have been trained by fishermen. In Japan, traditional forms of it can be seen on the Nagara River in the city of Gifu, Gifu Prefecture, where cormorant fishing has continued uninterrupted for 1300 years, or in the city of Inuyama, Aichi. In Guilin, China, cormorant birds are famous for fishing on the shallow Lijiang River.

A snare is tied near the base of the bird's throat, which allows the bird only to swallow small fish. When the bird captures and tries to swallow a large fish, the fish is caught in the bird's throat. When the bird returns to the fisherman's raft, the fisherman helps the bird to remove the fish from its throat. The method is not as common today, since more efficient methods of catching fish have been developed.

[edit] Cultural references

"Thence up he flew, and on the Tree of Life,
The middle Tree and highest there that grew,
Sat like a Cormorant; yet not true Life
Thereby regaind, but sat devising death
To them who liv'd; [...]"

-John Milton, Paradise Lost, Book IV, lines 194-98

"The common cormorant or shag
Lays eggs inside a paper bag,
The reason you will see no doubt
It is to keep the lightning out.
But what these unobservant birds
Have never noticed is that herds
Of wandering bears may come with buns
And steal the bags to hold the crumbs."
The Cormorant in Its Element
That bony potbellied arrow, wing-pumping along
implacably, with a ramrod's rigid adherence,
airborne, to the horizontal, discloses talents
one would never have guessed at. Plummeting
waterward, big black feet splayed for a landing
gear, slim head turning and turning, vermilion-
strapped, this way and that, with a lightning glance
over the shoulder, the cormorant astounding-
ly, in one sleek involuted arabesque, a vertical
turn on a dime, goes into the inimitable
vanishing-and-emerging-from-under-the-briny-
deep act which, unlike the works of Homo Houdini,
is performed for reasons having nothing at all
to do with ego, guilt, ambition, or even money.