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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

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 Britainmarker, Phalacrocorax carbo (now referred to by ornithologists as the Great Cormorant) and P. aristotelis (the European 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 Zealandmarker (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 attach 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. The French explorer André Thévet commented in 1558 that "...the beak [is] similar to that of a cormorant or other corvid," which demonstrates that the erroneous belief that the birds were related to ravens lasted at least to the 16th century.

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 lb). The recently-extinct Spectacled Cormorant (Phalacrocorax perspicillatus) was rather larger, at an average size of 6.3 kg (14 lb). 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 Zealandmarker) 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.

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 Pacificmarker 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. All cormorants have preen gland secretions that are used ostensibly to keep the feathers waterproof. Some sources state that cormorants have waterproof feathers while others say that they have water permeable feathers. Still others suggests that the outer plumage absorbs water but does not permit it to penetrate the layer of air next to the skin. The wing drying action is seen even in the flightless cormorant but commonly in the Antarctic shags and red-legged cormorants. Alternate functions suggested for the spread-wing posture include that it aids thermoregulation, digestion, balances the bird or indicates presence of fish. A detailed study of the Great Cormorant concludes that it is without doubt to dry the plumage.

Cormorants are colonial nesters, using trees, rocky islets, or cliffs. The egg 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.

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 and Ahlquist's "pan-Ciconiiformes" - remain mostly unresolved.

Notwithstanding, 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. 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 extreme case be reduced to the Great, White-breasted and Temminck's Cormorants.

Pending a thorough review of the Recent and prehistoric cormorants, the single-genus approach is followed here for three reasons: First, it is preferable 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, making it easier to incorporate data on status and conservation. In accordance with the treatment there, the Imperial Shag complex is here left unsplit too, but the King Shag complex is 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" does indeed have some degree of merit - though not as originally intended - but fails to account for basal lineages and the fact that the entire family cannot be clearly divided at present beyond the superspecies or species-complex level. The resolution provided by the mtDNA 12S rRNA and ATPase subunit 6 and 8 sequence data 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 Pacificmarker species especially - on the DNA sequence data are unstudied.

Species in HBW sequence

Cormorant (species unknown) begins its dive
Immature Phalacrocorax atriceps albiventer
This sequence follows the Handbook of Birds of the World.

Species in phylogenetic sequence

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

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. They often have a diminutive frontal tuft.


Basal lineage 2: Red-footed Shag. Included in Leucocarbo or Stictocarbo ("Leucocarboninae")
Pacific coast of South America. This species apparently has no close living relatives. It has a highly apomorphic color pattern: naked red base of bill, red feet, and a white neck spot, and it is crestless. It seems to be convergent in some aspects with the punctatus superspecies. What seems sure by now is that this species must be placed in a distinct monotypic genus Poikilocarbo in almost any case, if any species are split from Phalacrocorax at all.


Blue-eyed shags and relatives: variously placed in Euleucocarbo, Hypoleucos, Leucocarbo, Notocarbo and Stictocarbo ("Leucocarboninae"), and the monotypic Nannopterum.
This reasonably well-supported marine clade contains 3 lineages:
#One containing American species which are mainly black-footed, black-plumaged, and have yellow skin at the base of the bill as well as white display crests behind the eyes in breeding plumage. They occur in marine and freshwater habitats. The Flightless Cormorant of the Galápagos Islandsmarker also seems to belong here. Its wings have been reduced by evolution to tiny size, it is extremely apomorphic due to its flightlessness, and its plumage is entirely nondescript. If considered a distinct genus, they would get the name Dilophalieus or (more probably) Nannopterum, the old genus of the Flightless Cormorant.
#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
#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. It 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 to this group. The genus name Leucocarbo would apply to either this group, or the entire clade.


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 Straitmarker to Californiamarker. They are black-footed and have white ornamental plumes strewn about the head and neck in breeding plumage. They 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.
A group of black-footed species occurring in tropical coastal or inland habitat between the Persian Gulfmarker 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 included in recent research are quite dissimilar; the three unstudied ones 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 Zealandmarker 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 from the all-black plumage, looks almost identical to that long-extinct bird.


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


Evolution and fossil record

Cormorants seem to be a very ancient group, with similar ancestors reaching all the way back to the time of the dinosaurs. In fact, the very earliest known modern bird, Gansus yumenensis, had essentially the same structure, although it was not a cormorant per se. The details of the evolution of the cormorant are mostly unknown. Even the technique of using the distribution and relationships of a species to figure out where it came from, biogeography, usually very informative, does not give very specific data for this probably rather ancient and widespread group. However, the closest living relatives of the cormorants and shags are the other families of the suborder Sulae—darters and gannets and boobies—which have a primarily Gondwanan distribution. Hence, at least the modern diversity of Sulae probably originated in the southern hemispheremarker.

While the leucocarbonines are almost certainly of southern Pacific origin—possibly even the 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 with the Phalacrocoracidae:

A scapula from the Campanian-Maastrichtian boundary, about 70 mya (million years ago), was found in the Nemegt Formation in Mongoliamarker; it is now in the PINmarker collection. It is from a bird roughly the size of a Spectacled Cormorant, and quite similar to the corresponding bone in Phalacrocorax. A Maastrichtian (Late Cretaceous, c.66 mya) right femur, AMNHmarker FR 25272 from the Lance Formation near Lance Creek, Wyomingmarker, 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.

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 near certainty is that AMNH FR 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.

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 eastern, south-eastern or southern 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.

Two distinct genera of prehistoric cormorants are widely accepted today, if Phalacrocorax is used for all living species:
  • Limicorallus (Indricotherium middle Oligocene of Chelkar-Teniz, Kazakhstan)
  • Nectornis (Late Oligocene?/Early Miocene of C Europe - Middle Miocene of Bes-Konak, Turkey) - includes Oligocorax miocaenus


The proposed genus Oligocorax appears to be paraphyletic - the European species have been separated in Nectornis, and the North American ones are placed in the expanded Phalacrocorax. A Late Oligocene fossil cormoran foot from Enspelmarker (Germany), sometimes placed herein, would then be referable 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 conform with them in size and seem to have inhabited the same habitat: subtropical coastal or inland waters. Limicorallus, meanwhile, was initially believed to be a rail or a dabbling duck by some. There are also undescribed remains of apparent cormorants from the Quercy Phosphorites of Quercy (Francemarker), dating to some time between the Late Eocene and the mid-Oligocene.

Some other Paleogene remains are sometimes assigned to the Phalacrocoracidae, but these birds seem quite intermediate between cormorants and darters (and lack clear autapomorphies of either). Thus, they may be quite basal members of the Palacrocoracoidea. The taxa in question are:
  • Piscator (Late Eocene of England)
  • "Pelecaniformes" gen. et sp. indet. (Jebel Qatrani Early Oligocene of Fayum, Egypt) – similar to Piscator?
  • Borvocarbo (Late Oligocene of C Europe)


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

The remaining species are, in accordance with the scheme used in this article, all placed in the modern genus Phalacrocorax:
  • Phalacrocorax marinavis (Oligocene ?-? Early Miocene of Oregon, USA) - formerly Oligocorax
  • Phalacrocorax littoralis (Late Oligocene/Early Miocene of St-Gérand-le-Puy, France) - formerly Oligocorax, might belong into Nectornis
  • Phalacrocorax intermedius (Early - Middle Miocene of C Europe) - includes P. praecarbo, Ardea/P. brunhuberi and Botaurites avitus
  • Phalacrocorax macropus (Early Miocene ?-? Pliocene of NW USA)
  • Phalacrocorax ibericus (Late Miocene of Valles de Fuentiduena, Spain)
  • Phalacrocorax lautus (Late Miocene of Golboçica, Moldavia)
  • Phalacrocorax serdicensis (Late Miocene of Hrabarsko, Bulgaria)
  • Phalacrocorax femoralis (Modelo Late Miocene/Early Pliocene of WC North America) - formerly Miocorax
  • Phalacrocorax sp. (Late Miocene/Early Pliocene of Lee Creek Mine, USA)
  • Phalacrocorax longipes (Late Miocene - Early Pliocene of the Ukraine) - formerly Pliocarbo
  • Phalacrocorax goletensis (Early Pliocene ?-? Early Pleistocene of Mexico)
  • Phalacrocorax wetmorei (Bone Valley Early Pliocene of Florida)
  • Phalacrocorax sp. (Bone Valley Early Pliocene of Polk County, Florida, USA)
  • Phalacrocorax leptopus (Juntura Early/Middle Pliocene of Junturamarker, Malheur Countymarker, Oregonmarker, USA)
  • Phalacrocorax idahensis (Middle Pliocene ?-? Pleistocene of Idaho, USA)
  • Phalacrocorax destefanii (Late Pliocene of Italy) - formerly Paracorax
  • Phalacrocorax filyawi (Pinecrest Late Pliocene of Florida, USA) - may be P. idahensis
  • Phalacrocorax kumeyaay (San Diego Late Pliocene of California)
  • Phalacrocorax macer (Late Pliocene of Idaho, USA)
  • Phalacrocorax mongoliensis (Late Pliocene of W Mongolia)
  • Phalacrocorax rogersi (Late Pliocene -? Early Pleistocene of California, USA)
  • Phalacrocorax kennelli (San Diego Pliocene of California)
  • Phalacrocorax sp. "Wildhalm" (Pliocene) - may be same as P. longipes
  • Phalacrocorax chapalensis (Late Pliocene/Early Pleistocene of Jalisco, Mexico
  • Phalacrocorax gregorii (Late Pleistocene of Australia) - possibly not a valid species
  • Phalacrocorax vetustus (Late Pleistocene of Australia) - formerly Australocorax, possibly not a valid species
  • Phalacrocorax reliquus
  • Phalacrocorax sp. (Sarasota County, Florida) - may be P. filawyi/idahensis


The former "Phalacrocorax" (or "Oligocorax") mediterraneus is now considered to belong to the bathornithid Paracrax antiqua. "P." subvolans was actually a darter (Anhinga).

Cormorant fishing

A Chinese fisherman with his two cormorants


Humans have historically exploited cormorants' fishing skills, in Chinamarker, Japanmarker, and Macedoniamarker, where they have been trained by fishermen. 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.

In Japan, cormorant fishing is called ukai (鵜飼). Traditional forms of ukai can be seen on the Nagara Rivermarker in the city of Gifu, Gifu Prefecturemarker, where cormorant fishing has continued uninterrupted for 1300 years, or in the city of Inuyama, Aichimarker. In Guilinmarker, China, cormorant birds are famous for fishing on the shallow Lijiang River.

In Gifu, the Japanese Cormorant (P. capillatus) is used; Chinese fishermen often employ Great Cormorants (P. carbo).

Cormorants in human culture

  • Cormorants feature quite commonly in heraldry and medieval ornamentation, usually in their "wing-drying" pose, which was seen as representing the Christian cross. For example, the Norwegian municipalities of Røstmarker, Loppamarker and Skjervøymarker have cormorants in their coat-of-arms. The species depicted in heraldry is most likely to be the Great Cormorant, the most familiar species in Europe.
  • In 1853, a woman wearing a dress made of cormorant feathers was found on San Nicolas Islandmarker, off the southern coast of Californiamarker. She had sewn the feather dress together using whale sinews. She is known as the Lone Woman of San Nicolas and was later baptized "Juana Maria" (her original name is lost). The woman had lived alone on the island for 18 years before being rescued.
  • In addition to those mentioned above, the bird has inspired numerous writers, including Amy Clampitt, who wrote a poem called "The Cormorant in its Element". Which species she was referring to is not obvious, since all members of the family share the characteristic behavioural and morphological features that the poem celebrates. The combination of "slim head [...] vermilion-strapped" and "big black feet" perhaps points at the Pelagic Cormorant, which is the only species occurring in the temperate U.S. with these features.
  • The cormorant as a symbol of deception and greed is described in Milton's Paradise Lost, sitting on the Tree of Life, as an image of Satan entering Paradise in disguise before tempting Eve.
  • There is a cormorant portrayed in the first of the fictional paintings by Jane Eyre in Charlotte Bronte's novel, representing Blanche Ingram.
  • The mythical Liver Bird symbol of Liverpool is commonly thought to be a cross between an eagle and a comorant.


Footnotes

References

  • (1972): The Mochica: A Culture of Peru. Praeger Press, New York.
  • (1997):. The Spirit of Ancient Peru: Treasures from the Museo Arqueológico Rafael Larco Herreramarker. Thames and Hudson, New York.
  • (1971): Systematics and evolution of the Gruiformes (Class Aves). 2. Additional comments on the Bathornithidae, with descriptions of new species. American Museum Novitates 2449: 1-14 PDF fulltext
  • (1979): Family Phalacrocoracidae. In: : Check-List of the Birds of the World Vol. 1, 2nd ed. (Struthioniformes, Tinamiformes, Procellariiformes, Sphenisciformes, Gaviiformes, Podicipediformes, Pelecaniformes, Ciconiiformes, Phoenicopteriformes, Falconiformes, Anseriformes): 163-179. Museum of Comparative Zoology, Cambridge.
  • (2002): The Mesozoic radiation of Neornithes. In: : Mesozoic Birds: Above the Heads of Dinosaurs: 339-388. ISBN 0520200942
  • (1932): A New Species of Cormorant from Pliocene Deposits near Santa Barbara, California. Condor 34(3): 118-120. PDF fulltext DjVu fulltext
  • (2007): 2007 IUCN Red List of Threatened Species. IUCN, Gland.
  • (2000): The Phylogenetic Relationships of the Shags and Cormorants: Can Sequence Data Resolve a Disagreement between Behavior and Morphology? Molecular Phylogenetics and Evolution 17(3): 345-359. PDF fulltext
  • (1995): Synopsis of Mesozoic birds and early evolution of Class Aves. Archaeopteryx 13: 47–66. PDF fulltext
  • (2005): Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae). Journal of Zoological Systematics 43(1): 67-71. PDF fulltext
  • (1970): A Redescription of Two Pliocene Cormorants. Condor 72(3): 293-298. PDF fulltext DjVu fulltext
  • (1992): Family Phalacrocoracidae. In: (eds.): Handbook of Birds of the World, Volume 1 (Ostrich to Ducks): 326-353, plates 22-23. Lynx Edicions, Barcelona. ISBN 84-87334-10-5
  • (1998): Book of Humorous Quotations. Wordsworth Editions. ISBN 1853267597 Limited fulltext at Google Books.
  • (1988): Phylogeny of the Phalacrocoracidae. Condor 90(4): 885–905. PDF fulltext DjVu fulltext
  • (1558): [About birds of Ascension Island]. In: Les singularitez de la France Antarctique, autrement nommee Amerique, & de plusieurs terres & isles decouvertes de nostre temps: 39-40. Maurice de la Porte heirs, Paris. Fulltext at Gallica
  • (1976): Australasia and the origin of shags and cormorants, Phalacrocoracidae. Proceedings of the XVI International Ornithological Congress: 121–124.


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