Cormorant

For other uses, see Cormorant (disambiguation).
Cormorants and shags
Temporal range: Late Cretaceous? – Recent
Little pied cormorant
Phalacrocorax melanoleucos
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neoaves
Order: Suliformes
Family: Phalacrocoracidae
Reichenbach, 1850
Genus: Phalacrocorax (but see text)
Brisson, 1760
Species

3–43, see text

Synonyms

Australocorax Lambrecht, 1931
Compsohalieus B. Brewer & Ridgway, 1884
Cormoranus Baillon, 1834
Dilophalieus Coues, 1903
Ecmeles Gistel, 1848
Euleucocarbo Voisin, 1973
Halietor Heine, 1860
Hydrocorax Vieillot, 1819 (non Brisson, 1760: preoccupied)
Hypoleucus Reichenbach, 1852
Leucocarbo Bonaparte, 1857
Microcarbo Bonaparte, 1856
Miocorax Lambrecht, 1933
Nannopterum Sharpe, 1899
Nesocarbo Voisin, 1973
Notocarbo Siegel-Causey, 1988
Pallasicarbo Coues, 1903
Paracorax Lambrecht, 1933
Poikilocarbo Boetticher, 1935
Pliocarbo Tugarinov, 1940
Stictocarbo Bonaparte, 1855
Viguacarbo Coues, 1903
(but see text)

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", and 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.

Names

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"). 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 André Thévet 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.

Characteristics

European shag with hooked bill
Two double-crested cormorants. The one on the right has captured a fish.
Imperial shags in Beagle Channel
A Cormorant relaxes by perching on the bank of kanjia lake
Great cormorant in Hyogo, Japan

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,[2] commentary [3] and existing reference video [4]). 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[5] state that cormorants have waterproof feathers while others say that they have water permeable feathers.[6][7] Still others suggests that the outer plumage absorbs water but does not permit it to penetrate the layer of air next to the skin.[8] The wing drying action is seen even in the flightless cormorant but commonly in the Antarctic shags[9] and red-legged cormorants. Alternate functions suggested for the spread-wing posture include that it aids thermoregulation,[10] digestion, balances the bird or indicates presence of fish. A detailed study of the great cormorant concludes that it is without doubt[11] to dry the plumage.[12][13]

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.

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 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.[14]

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.[15]

Pending a thorough review of the Recent and prehistoric cormorants, the single-genus approach[16] 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,[17] 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) shags[18] 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.[19] The resolution provided by the mtDNA 12S rRNA and ATPase subunits six and eight sequence data[19] 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.

Its traditional scientific name is the literal Latinised Ancient Greek equivalent of the common name: Phalacrocorax is an ancient term for cormorants; literally, it means "bald raven", from falakrós (φᾶλακρός, bald) + kórax[20] (κόραξ, raven).[21]

Species in HBW taxonomic sequence

Three cormorants sitting high on a tree by the River Medway in Kent, England
Cormorant (species unknown) begins its dive
Immature Phalacrocorax atriceps albiventer
Phalacrocorax niger in Hyderabad, India
Guanay cormorant (Phalacrocorax bougainvillii) at Weltvogelpark Walsrode

This sequence follows the Handbook of the Birds of the World.[16]

Species in phylogenetic sequence

Little cormorant, Phalacrocorax niger
Red-legged cormorant (Phalacrocorax gaimardi)

This list attempts to follow a phylogenetic order.[22] 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-legged cormorant. Included in Leucocarbo or Stictocarbo ("Leucocarboninae")

Pacific coast of South America. This species apparently has no close living relatives. It has a highly apomorphic colour 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 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.[23]
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"), and the monotypic Nannopterum.

This reasonably well-supported marine clade contains three 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 Islands also seems to belong here. Its wings have been reduced by evolution to a 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.
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. 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.

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 included in recent research[19] are quite dissimilar; the three unstudied ones are very similar to one or the other.[16]

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 from the all-black plumage, looks 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

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 back to the time of the dinosaurs. In fact, the earliest known modern bird, Gansus yumenensis, had essentially the same structure. 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 hemisphere.

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 Mongolia; it is now in the PIN collection.[25] 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, AMNH FR 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.[26]

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 indisputable neornithine features, it is not entirely certain that the bone is correctly referred to this group.[27]

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.

Double-crested cormorant in its natural habitat

Two distinct genera of prehistoric cormorants are widely accepted today, if Phalacrocorax is used for all living species:

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 cormorant foot from Enspel, 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 (France), 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:

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:

The former "Phalacrocorax" (or "Oligocorax") mediterraneus is now considered to belong to the bathornithid Paracrax antiqua.[30] "P." subvolans was actually a darter (Anhinga).

Cormorant fishing

A Chinese fisherman with his two cormorants
Japanese man performing the ancient cormorant night fishing technique.
Main article: Cormorant fishing

Humans have used cormorants' fishing skills in China, Japan, Greece and the Republic of Macedonia, 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 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, cormorants 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).[31]

Cormorants in human culture

Cormorant fur coat

See also

Footnotes

  1. ↑ Elliott KH, Ricklefs RE, Gaston AJ, Hatch SA, Speakman JR, Davoren GK. 2013. High flight costs and low dive costs support the biomechanical hypothesis for flightlessness in penguins. PNAS 110:9380-9384.
  2. ↑ http://www.nwdiveclub.com/download/file.php?id=22712&mode=view
  3. ↑ http://www.nwdiveclub.com/viewtopic.php?f=11&t=22970
  4. ↑ http://www.wcs.org/news-and-features-main/cormorant-deep-sea-dive.aspx
  5. ↑ Cramp S, Simmons KEL (1977) Handbook of the Birds of the Western Palearctic Volume 1, Oxford University Press ISBN 0198573588
  6. ↑ Rijke AM (1968). "The water repellency and feather structure of cormorants, Phalacrocoracidae". J. Exp. Biol. 48: 185–189.
  7. ↑ Marchant S. M. and Higgins, P. J. (1990). Handbook of Australian, New Zealand and Antarctic Birds. Vol 1A. Oxford University Press.
  8. ↑ Hennemann, W. W., III (1984). "Spread-winged behaviour of double-crested and flightless cormorants Phalacrocorax auritus and P. harrisi: wing drying or thermoregulation?". Ibis 126 (2): 230–239. doi:10.1111/j.1474-919X.1984.tb08002.x.
  9. ↑ Cook, Timothee R & Guillaume Leblanc (2007). "Why is wing-spreading behaviour absent in blue-eyed shags?" (PDF). Animal Behaviour 74 (3): 649–652. doi:10.1016/j.anbehav.2006.11.024.
  10. ↑ Curry-Lindahl, K (1970). "Spread-wing postures in Pelecaniformes and Ciconiiformes" (PDF). Auk 87 (2): 371–372. doi:10.2307/4083936.
  11. ↑ Sellers, R. M. (1995). "Wing-spreading behavior of the cormorant Phalacrocorax carbo" (PDF). Ardea 83: 27–36.
  12. ↑ Nelson, J. Bryan (2005). Pelicans, Cormorants and Their Relatives: Pelecanidae, Sulidae, Phalacrocoracidae, Anhingidae, Fregatidae, Phaethontidae. Oxford University Press. pp. 162–163. ISBN 0-19-857727-3.
  13. ↑ Bernstein, N. P & S J Maxson (1982). "Absence of Wing-spreading Behavior in the Antarctic Blue-eyed Shag (Phalacrocorax Atriceps Bransfieldensis)" (PDF). The Auk 99 (3): 588–589.
  14. ↑ Kennedy et al. (2000), Mayr (2005)
  15. ↑ See Siegel-Causey (1988), Orta (1992) and Kennedy et al. (2000) for a review of classification schemes.
  16. 1 2 3 Orta (1992)
  17. ↑ IUCN (2007)
  18. ↑ van Tets (1976), Siegel-Causey (1988)
  19. 1 2 3 Kennedy et al. (2000)
  20. ↑ Modern Greek: koráki (κοράκι)
  21. ↑ Woodhouse (1910)
  22. ↑ Based on Orta (1992) and Kennedy et al. (2000). Applicable genus names are from Dorst & Mougin (1979) and Orta (1992)
  23. ↑ Much of Phalacrocoracidae systematics hinges upon this most enigmatic species. The white neck spots and general colouration are very much unlike that of any other living cormorant, though anatomically it is quite similar to the species composing the punctatus superspecies, which are also the only other members of this family with a grey background colour. No satisfying theory has been proposed to explain this oddity.
  24. ↑ According to Dorst & Mougin (1979), close to the Cape cormorant and possibly the spotted group. Orta (1992) disagrees – see HBW sequence above – but does not give details. As this species and the cape cormorant occupy ranges that almost entirely overlap, it is not too likely that they are closely related. If they were, their ancestors would probably have at one time been restricted to refugia and afterwards, expanding their ranges again, evolved into a striking case of character displacement.
  25. ↑ Kurochkin (1995)
  26. ↑ Hope (2002)
  27. ↑ Hope (2002) and see Hesperornithes
  28. ↑ A proximal ulna, Specimen PB 311, Pierce Brodkorb collection. Initially assigned to P. idahensis. However, it is far too large, being from a very big species possibly larger than a great cormorant: Murray (1970)
  29. ↑ At least part of a coracoid is known. Does not appear to belong to the true cormorants. May have been closer in habitus to North Pacific shags, but not closely related to these: Howard (1932).
  30. ↑ Cracraft (1971)
  31. ↑ Cormorant Fishing "UKAI". Version of May, 2001. Retrieved 2008-JAN-30.

References

External links

Wikimedia Commons has media related to Phalacrocoracidae and Phalacrocorax.
Look up cormorant in Wiktionary, the free dictionary.
This article is issued from Wikipedia - version of the Monday, May 02, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.