Cormorant

Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the International Ornithologists' Union adopted a consensus taxonomy of seven genera. The great cormorant and the common shag are the only two species of the family commonly encountered in Britain and Ireland, and the names "cormorant" and "shag" have been later assigned to different species in the family somewhat haphazardly.
Cormorants and shags are medium-to-large birds, with body weight in the range of and wing span of. The majority of species have dark feathers. The bill is long, thin and hooked. Their feet have webbing between all four toes. All species are fish-eaters, catching the prey by diving from the surface. They are excellent divers, and under water they propel themselves with their feet with help from their wings; some cormorant species have been found to dive as deep as. Cormorants and shags have relatively short wings due to their need for economical movement underwater, and consequently have among the highest flight costs of any flying bird.
Cormorants nest in colonies around the shore, on trees, islets or cliffs. They are coastal rather than oceanic birds, and some have colonised inland waters. The original ancestor of cormorants seems to have been a freshwater bird. They range around the world, except for the central Pacific islands.
Cormorants might have been a freshwater species from south Asia. From there, they spread around the Eurasian landmass and the world.

Names

"Cormorant" is a contraction probably derived from Latin corvus marinus, "sea raven"; in the early 19th century, the similarly derived spelling "corvorant" was sometimes used. Cormoran is the Cornish name of the sea giant in the tale of Jack the Giant Killer. 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: "the beak 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.
No consistent distinction exists between cormorants and shags. The names "cormorant" and "shag" were originally the common names of the two species of the family found in Ireland and also in Great Britain Phalacrocorax carbo and Gulosus aristotelis. "Shag" refers to the bird's crest, which is conspicuous in the European shag, but less so in the great cormorant. As other species were encountered by English-speaking sailors and explorers elsewhere in the world, some were called cormorants and some shags, sometimes 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; for example, all species in the family which occur in New Zealand are known locally as shags, including four non-endemic species known as cormorant elsewhere in their range. In 1976, Gerard Frederick van Tets proposed to divide the family into two genera and attach the name "cormorant" to one and "shag" to the other, but this nomenclature has not been widely adopted.

Description

Cormorants and shags are medium-to-large seabirds. They range in size from the pygmy cormorant, at as little as and, to the flightless cormorant, at a maximum size and. The recently extinct spectacled cormorant was rather larger, at an average size of. Nearly all the Northern Hemisphere species have mainly dark plumage, but many Southern Hemisphere species are black and white, and a few are quite colourful. Many species have areas of coloured skin on the face 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.

Habitat

Habitat varies from species to species: some are restricted to seacoasts, while others occur in both coastal and inland waters to varying degrees. They range around the world, except for the central Pacific islands.

Behaviour

All cormorants and shags 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, though some also propel themselves with their wings. Imperial shags fitted with miniaturized video recorders have been filmed diving to depths of as much as to forage on the sea floor.
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 suggest 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 not in the Antarctic shags or red-legged cormorants. Alternate functions suggested for the spread-wing posture include that it aids thermoregulation or digestion, balances the bird, or indicates presence of fish. A detailed study of the great cormorant concluded there is little doubt that it serves to dry the plumage.
Cormorants are colonial nesters, using trees, rocky islets, or cliffs. The eggs are a chalky-blue colour. There is usually one brood a year. Parents regurgitate food to feed their young.

Taxonomy

The genus Phalacrocorax, from which the family name Phalacrocoracidae is derived, is Latinised from Ancient Greek φαλακρός phalakros "bald" and κόραξ korax "raven". This is thought to refer to the ornamental white head plumes prominent in Mediterranean birds of this species, or the creamy white patch on the cheeks of adult great cormorants, but is certainly not a unifying characteristic of cormorants.
The cormorant family was traditionally placed within the Pelecaniformes or, in the Sibley–Ahlquist taxonomy of the 1990s, the expanded Ciconiiformes. Pelecaniformes in the traditional sense—all waterbird groups with totipalmate foot webbing—are not a monophyletic group, even after the removal of the distantly-related tropicbirds. 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, and perhaps the pelicans or even penguins, than to all other living birds.
In recent years, three preferred treatments of the cormorant family have emerged: either to leave all living cormorants in a single genus, Phalacrocorax, or to split off a few species such as the imperial shag complex 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 Japanese cormorants. In 2014, a landmark study proposed a 7 genera treatment, which was adopted by the IUCN Red List and BirdLife International, and later by the IOC in 2021, standardizing it.
The cormorants and the darters have a unique bone on the back of the top of the skull known as the os nuchale or occipital style which was called a xiphoid process in early literature. This bony projection provides anchorage for the muscles that increase the force with which the lower mandible is closed. This bone and the highly developed muscles over it, the M. adductor mandibulae caput nuchale, are unique to the families Phalacrocoracidae and Anhingidae.
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 cormorants and Leucocarbo sensu lato shags does have some degree of merit. The resolution provided by the mtDNA 12S rRNA and ATPase subunits six and eight sequence data is not sufficient to resolve several groups to satisfaction properly; in addition, many species remain unsampled, the fossil record has not been integrated in the data, and the effects of hybridisation – known in some Pacific species especially – on the DNA sequence data are unstudied.
A multigene molecular phylogenetic study published in 2014 provided a genus-level phylogeny of the family; this is now followed by most authorities, including the IOC World Bird List.

List of genera

As per the IOU, the IUCN Red List and BirdLife International, the family contains 7 genera:

Image	Genus	Species
	Microcarbo Bonaparte, 1856	Crowned cormorant Microcarbo coronatus Little cormorant Microcarbo niger Little pied cormorant Microcarbo melanoleucos Pygmy cormorant Microcarbo pygmeus Reed cormorant or long-tailed cormorant Microcarbo africanus †Serventys' cormorant Microcarbo serventyorum Around Indian Ocean, one species extending from Central Asia into Europe. Mostly in freshwater habitat. Small, nondescript black to dark brown.
	Poikilocarbo Boetticher, 1935	Red-legged cormorant Poikilocarbo gaimardi Subtropical to subantarctic Pacific South America, ranging a bit into the southwestern Atlantic. Maritime. Mid-sized, grey with scalloped wings and contrasting white/yellow/red neck mark and bare parts. Its high-pitched chirping calls are quite unlike those of other cormorants.
	Urile Bonaparte, 1855	Brandt's cormorant Urile penicillatus Red-faced cormorant Urile urile Pelagic cormorant Urile pelagicus Spectacled cormorant †Urile perspicillatus Northern Pacific, one species extending into subtropical waters on the American West Coast. Maritime. Smallish to large, generally black with metallic sheen, in breeding plumage with bright bare facial skin in the eye region and two crests.
	Phalacrocorax Brisson, 1760	Bank cormorant Phalacrocorax neglectus Socotra cormorant Phalacrocorax nigrogularis Pitt shag Phalacrocorax featherstoni Spotted shag Phalacrocorax punctatus Black-faced cormorant Phalacrocorax fuscescens Australian pied cormorant Phalacrocorax varius Little black cormorant Phalacrocorax sulcirostris Indian cormorant Phalacrocorax fuscicollis Cape cormorant Phalacrocorax capensis Japanese cormorant or Temminck's cormorant Phalacrocorax capillatus Great cormorant Phalacrocorax carbo Mostly around the Indian Ocean, one species group extending throughout Eurasia and to Atlantic North America. Maritime to freshwater. Size very variable, blackish with metallic sheen and/or white cheek and thigh patches or underside at least in breeding plumage; usually a patch of bare yellow skin at the base of the bill.
	Gulosus Montagu, 1813	European shag Gulosus aristotelis Breeds in the European Arctic, winters in Europe and North Africa. Maritime. Mid-sized, glossy black, in breeding plumage with a forehead crest curled to the front.
	Nannopterum Sharpe, 1899	Flightless cormorant Nannopterum harrisi Neotropic cormorant Nannopterum brasilianum Double-crested cormorant Nannopterum auritum Throughout the Americas. Mostly freshwater. Smallish to large, nondescript brownish-black. One species with white tufts on sides of head in breeding plumage.
	Leucocarbo Bonaparte, 1856	Rock shag or Magellanic cormorant Leucocarbo magellanicus Guanay cormorant Leucocarbo bougainvillii Bounty shag Leucocarbo ranfurlyi New Zealand king shag or rough-faced shag Leucocarbo carunculatus Chatham shag Leucocarbo onslowi Stewart Island shag Leucocarbo chalconotus Auckland shag Leucocarbo colensoi Campbell shag Leucocarbo campbelli Imperial shag or blue-eyed shag Leucocarbo atriceps South Georgia shag Leucocarbo georgianus Crozet shag Leucocarbo melanogenis Antarctic shag Leucocarbo bransfieldensis Kerguelen shag Leucocarbo verrucosus Heard Island shag Leucocarbo nivalis Macquarie shag Leucocarbo purpurascens Generally Subantarctic, but extending farther north in South America; many oceanic-island endemics. Maritime. Smallish to largish, typically black above and white below, and with bare yellow or red skin in the facial region. A southern circumpolar group of several species is characterised by bright blue orbital skin.

Prior to 2021, the IOU classified all these species in just three genera: Microcarbo, Leucocarbo, and a broad Phalacrocorax containing all remaining species; however, this treatment rendered Phalacrocorax deeply paraphyletic with respect to Leucocarbo. Other authorities, such as the Clements Checklist, formerly recognised only Microcarbo as a separate genus from Phalacrocorax.