Cormorant Profile 2

by Lisa Wooten

Title

Cormorant Profile 2

Artist

Lisa Wooten

Medium

Photograph - Photographs

Description

Phalacrocoracidae is a family of some 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed. There is no consistent distinction between �cormorants� and �shags� as these appellations have been assigned to different species randomly.
Cormorants and shags are medium-to-large birds, with body weight in the range of 0.35�5 kilograms (0.77�11.02 lb) and wing span of 45�100 centimetres (18�39 in). 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 45 metres. They have relatively short wings due to their need for economical movement underwater, and consequently have the highest flight costs of any bird.1
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 � indeed, the original ancestor of cormorants seems to have been a fresh-water bird. They range around the world, except for the central Pacific islands.
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 Great Britain, 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 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 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 Latinised Ancient Greek, from φαλακρός (phalakros, �bald�) and κόραξ (korax, �raven�).2 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 either directly from Latin corvus marinus, �sea raven� or through Brythonic Celtic. 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 Andr� Th�vet commented in 1558, ��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.
A cormorant perching on the bank of Kanjia Lake, India
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 (39 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 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.
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, though some also propel themselves with their wings (see the picture,3 commentary 4 and existing reference video 5). 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 sources6 state that cormorants have waterproof feathers while others say that they have water permeable feathers.78 Still others suggests that the outer plumage absorbs water but does not permit it to penetrate the layer of air next to the skin.9 The wing drying action is seen even in the flightless cormorant but commonly in the Antarctic shags10 and red-legged cormorants. Alternate functions suggested for the spread-wing posture include that it aids thermoregulation,11 digestion, balances the bird or indicates presence of fish. A detailed study of the great cormorant concludes that it is without doubt12 to dry the plumage.1314
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.
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 recognised 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 or even penguins, than to all other living birds.15
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 (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 Japanese cormorants.16
Pending a thorough review of the Recent and prehistoric cormorants, the single-genus approach17 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,18 making it easier to incorporate data on status and conservation. In accordance with the treatment there, the imperial shag complex is here left unsplit as well, but the king shag complex has been.
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) shags19 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.20 The resolution provided by the mtDNA 12S rRNA and ATPase subunits six and eight sequence data20 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 hybridisation � known in some Pacific species especially � on the DNA sequence data are unstudied. Wikipedia

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March 6th, 2017

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