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Australian raven

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Australian raven
Australian National Botanic Gardens, Canberra, ACT
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Passeriformes
Family:
Corvidae
Genus:
Corvus
Species:
C. coronoides
Binomial name
Corvus coronoides
Subspecies
C. c. coronoides
C. c. perplexus
Synonyms

Corvus affinis Brehm, 1845
Corvus marianae Mathews, 1911
Corvus difficilis Stresemann, 1943

The Australian raven (Corvus coronoides) is a passerine bird in the crow family native to much of southern and northeastern Australia. Measuring 46–53 cm (18–21 in) in length, it has all-black plumage, beak and legs with white irises. Like those of the other two species of raven in Australia, its black feathers have grey bases. The Australian raven is further distinguished by its prominent throat hackles. Two subspecies are recognised, which differ slightly in calls and are quite divergent genetically. Nicholas Aylward Vigors and Thomas Horsfield described it in 1827, its species name highlighting its similarity with the carrion crow (C. corone).

The preferred habitat is open woodland and transitional zones, and it has adapted well to urban environments and is a common city bird in Sydney, Canberra and Perth. In eastern Australia its range is strongly correlated with the presence of sheep. An omnivorous and opportunistic feeder, it eats a wide variety of plant and animal material, as well as food waste from urban areas.

Taxonomy and naming

The Australian raven was first described by Nicholas Aylward Vigors and Thomas Horsfield in 1827, in which they reported George Caley's early notes on the species from the Sydney district.[2] Its specific epithet coronoides "crow-shaped" is derived from the Greek corone/κορονη "crow" and eidos/ειδος "shape" or "form".[3] The two naturalists regarded the Australian raven as very similar in appearance to the carrion crow (C. corone) of Europe,[4] though they noted it was larger with a longer bill. They did not give it a common name.[2] The location that the type specimen was collected is not recorded, but thought to be in the Parramatta district.[5] In his 1865 Handbook to the Birds of Australia, John Gould noted a single species of corvid in Australia, Corvus australis, which he called the white-eyed crow. He used Johann Friedrich Gmelin's 1788 name,[a] which predated Vigors and Horsfield's description.[8] In 1877 Richard Bowdler Sharpe recognised two species, but recorded that the feather bases of the type specimen of C. coronoides were white. He named this the crow and C. australis (as Corone australis) the raven.[5] Scottish naturalist William Robert Ogilvie-Grant corrected this in 1912 after re-examining the type specimen, clarifying the species as C. coronoides (raven, and incorporating little and Tasmanian ravens) and C. cecilae (crow).[9]

Gregory Mathews described the western subspecies perplexus in 1912, naming it the southwestern crow and noting that it was smaller than the nominate subspecies. He called C. coronoides coronoides the eastern crow, listing its range as New South Wales, and described what is now the Australian crow as another subspecies, C. coronoides cecilae, calling it the north-western crow and recording its range as northwestern Australia. In the same work he listed the raven as Corvus marianae, with a type specimen from Gosford and listing its range as New South Wales. He listed the little raven and forest raven as subspecies.[10] Mathews had erected C. marianae in 1911 as the name after declaring Corvus australis Gould to be preoccupied.[11]

Although called a raven, its closest affinities lie with the other four species of Australian corvid, which include the Torresian crow and little crow as well as the forest raven and little raven.[12] Initial single gene genetic analysis of the genus using mitochondrial DNA showed the three raven species to belong to one lineage and the two crows to another. The genetic separation between species is small and there was a suggestion the little raven may be nested within the Australian raven, though the authors conceded more genetic work was needed.[13] Subsequent multigene analysis using nuclear DNA by Jønsson and colleagues in 2012 showed the eastern and western subspecies of the Australian raven to form two clades, almost as genetically distinct as the Forest and little raven are to each other. This led the authors to propose the subspecies be recognised as separate species.[14]

Ian Rowley proposed that the common ancestor of the five species diverged into a tropical crow and temperate raven sometime after entering Australia from the north. The raven diverged into the ancestor of the forest and little ravens in the east and Australian raven in the west. As the climate was cooler and dryer, the aridity of central Australia split them entirely. Furthermore, the eastern diverged into nomadic little ravens and, in forested refuges, forest ravens. As the climate eventually became warmer, the western ravens spread eastwards and outcompeted forest ravens on mainland Australia. Rowley noted that the western ravens had features intermediate between Australian and little ravens.[15]

Alternative names sometimes seen include southern raven, southern crow and Kelly,[4] the last thought to have alluded to the Kelly Gang though did not appear until the 1920s. Southern crow was considered by the RAOU before Australian raven was adopted as the official name for the species in 1926.[16] The term "crow" is colloquially applied to any or all species of Australian corvid.[5] The Australian raven was called wugan by the local Eora and Darug inhabitants of the Sydney basin.[17]

Two subspecies are recognised:

  • C. c. coronoides, the nominate or eastern subspecies, is found across most of eastern Australia.[4] Its range is also highly correlated with the presence of sheep. This is thought to be because of the frequency of dead animals, which are an important source of food.[5]
  • C. c. perplexus, the western subspecies, occurs from the head of the Great Australian Bight in South Australia westwards into Western Australia where its northern limits are Shark Bay and the mulga-eucalypt boundary line.[4] It is less specialised in its habitat, as it does not share its distribution with the little raven, and does not appear to correlate with the range of sheep. Ornithologist Ian Rowley suggested the western populations may be older in origin as they lack the vigour of the eastern.[5] The western subspecies has a slightly lower-pitched call than that of the eastern subspecies,[18] with similarities to calls of the little raven. Of smaller size overall, it has shorter hackles and a more slender bill.[19] Intermediate birds are found in the Eyre Peninsula, Gawler Ranges and vicinity of Lake Eyre in South Australia.[4]

Description

In Sydney. Shows bare skin on neck
juvenile with dark eyes, Sydney

Measuring 46–53 cm (18–21 in) in length with a 100 cm (40 in) wingspan and weighing around 650 g (1.4 lb),[4] the adult Australian raven is an all black bird with black feet and beak. It has white irises each with a pale blue inner rim around the pupil. The plumage is glossy with a blue-purple to blue-green sheen, greenish over the ear coverts, depending on light. The underparts are not glossy.[20] The Australian raven has throat feathers (hackles) that are lanceolate with rounded tips, while the other four species have bifurcate tips, though this can be difficult to see in the field.[18] They are also longer than those of the other four species; when they are raised (such as when the bird is calling), they give the bird an unusual bearded appearance. The upper third of the upper mandible is covered with bristles. The long beak is heavy-set and is tipped with a slight hook.[20] It can be distinguished from the two species of crow occurring in Australia by the grey base of the feathers, which is white in the latter species. The demarcation between pale and black regions on the feather is gradual in the ravens and sharply delineated in the crows.[18] Unlike the other four species, the Australian raven has a bare patch of skin under, and extending to beside, the bill. This can be hard to discern in the field. The three species of raven are more heavily set with a broader chest than the two crow species, with the forest raven the stockiest of all.[21] Relative size of species is only useful when two species can be seen side by side, as the overlap in size is large and the difference in size small.[22]

Juveniles resemble adults, but have shorter throat hackles, and sometimes have a pink fleshy gape.[23] Their plumage is more ruffled and softer in appearance, lacks the glossy highlights and often having a brown tinge, and their bill is shorter.[20] Their eye colour varies with age, gradually lightening from juvenile to adult.[20] Nestlings up to four months old have blue-grey eyes, juveniles aged from four to fifteen months have brown eyes, and immature birds have hazel eyes with an inner blue rim around each pupil until age two years and ten months.[5]

Vocalisations

The territorial call of the Australian raven is a slow, high ah-ah-aaaah with the last note drawn out. It uses this call to communicate with other Australian ravens in the area.[12] When giving this call, the Australian raven has a horizontal posture, holding its head forward and body parallel to the ground, while perched on a prominent position. It ruffles its hackles and lowers its tail, and sometimes holds its beak open between calls. In contrast, the little raven and forest raven hold their bodies in an upright posture.[22] The five Australian species are very difficult to tell apart, with the call being the easiest way to do so,[4] although the drawing-out of the final note—long held to be solely recorded for the Australian raven—has been recorded for the other species and is hence not diagnostic of species.[22]

Distribution and habitat

The Australian raven is common throughout south-eastern Australia,[23] and southern Western Australia (the populations being connected by a narrow strip across the Nullarbor Plain), but it is rarer and more scattered in the north, with isolated sightings in Cape York at Coen, Windmill Creek and the Mitchell River,[24] and becoming more common south of Rockhampton. It is found throughout New South Wales, though is uncommon in the northeast of the state. It is rare in the Australian Alps, being replaced there by the little raven. It occurs across Victoria and eastern South Australia, through the Eyre Peninsula and Nullarbor Plain into Western Australia, across the state north to the Wooramel River.[25] It is found on some offshore islands such as Rottnest Island.[26] and Kangaroo Island.[25] It is a rare vagrant to Lord Howe Island.[25]

The Australian raven can be found in a wide range of natural and modified habitats. It requires available water and trees (or buildings) to roost in or perch on. Preferred habitats include eucalypt-dominated sclerophyll forest, and farmland adjacent to trees. It is also found in heath and mangroves. In areas where it occurs with the little raven, namely over much of central New South Wales, Victoria and into South Australia,[18] the Australian raven is restricted to more forested areas while the latter species prefers more open areas.[27] Similarly in inland Australia it can share range with the little crow as the two do not appear to compete. However, the ranges of similar-sized forest raven and Torresian crow only narrowly overlap with the Australian raven as all three compete with each other. In central and western regions, Australian ravens and Torresian crows vye for the scattered uncommon trees and outcrops, and only one or the other are found there.[5] It co-occurs with the forest raven in northeastern New South Wales from Port Stephens northwards.[18]

The Australian raven has adapted very well to human habitation in some cities and is a common bird in Canberra, Sydney and Perth; in Melbourne and Adelaide it is replaced as the common corvid by the little raven,[18] and by the Torresian crow in Brisbane.[citation needed]

Behaviour

Difficulties in distinguishing Australian corvids has hampered understanding of seasonal movements. The Australian raven is thought to be largely sedentary, with most movement of over 16 km due to flocks of non-breeding subadult birds.[28] Juvenile birds leave their parents and join flocks when they are four or five months old. Smaller flocks of 8–30 birds stay within an area of around 260 square kilometres, while larger flocks of up to 300 birds may travel hundreds of kilometres seeking food.[29]

A single breeding pair and their brood can occupy a territory of up to around 120 hectares and remains there year-round, though groups of ravens may enter this area to forage.[28] If the female dies, the male Australian raven replaces her and maintains the territory, while if the male bird is lost, the female abandons the territory.[30]

The Australian raven is a host for the channel-billed cuckoo (Scythrops novaehollandiae).

Australian ravens die most often by being shot, killed or poisoned. Despite their fondness for roadkill, fewer ravens are hit by vehicles than Australian magpies. Research in the 1950s and 60s showed that 64% of Australian ravens perished in their first year of life. Immature birds are most at risk of dying as they are more likely to come into conflict with farmers. Once they begin breeding at three years of age, they live another four to five years on average. During this time they produce two young each year.[30] The longest-lived Australian raven recorded is an adult that was banded and recovered 12 years and 5 months later.[29]

Australian ravens preen themselves frequently, particularly when roosting in the middle of the day. They also engage in allopreening, where birds will preen each others' head and neck. This takes place particularly in autumn, winter and spring and is important in pair bonding.[31]

Feeding

The Australian raven is omnivorous, though eats more meat than smaller corvids. Its diet in summer contains a high proportion of insects, while more plant items are eaten in autumn. Flesh makes up over half its diet in winter. Common invertebrates eaten include spiders, millipedes, centipedes (which ravens behead before eating), grasshoppers, cicadas and caterpillars (especially of the family Noctuidae), which are important in feeding nestlings. Australian ravens sometimes eat yabbies from the edges of dams. Unusually for a ground-feeding omnivore, earthworms are rarely eaten. They can kill birds as large as galahs and starlings. Most mammals are eaten as carrion, as many species are too large for the raven to kill.[32]

Foraging takes place in the mearly morning or late afternoon; birds rest in the hotter part of the day. Food is taken mainly from the ground; birds either finding objects while flying overhead, or by walking along and looking.[31] However, they occasionally feed in trees—Australian ravens forage eucalypt foliage for Christmas beetles.[32] If flying, they generally hold or snatch food with their bill, not their feet. Ravens also turn items on the ground (rocks or sticks) over or explore with their bill rather than use their feet.[31]

Australian ravens most often eat food where they find it unless taking food back for nestlings. Occasionally they have been observed caching carrion or a killed animal in a hole nearby to store it. They can pack shredded meat in their mouth under their tongue.[31]

Australian ravens have adapted well to eating rubbish and scraps in urban areas, such as school playgrounds, rubbish tips, bins outside supermarkets or restaurants, abbatoirs, piggeries and farmyards.[24] In one isolated study they were observed feeding on nectar from eucalypt flowers.[33]

Australian ravens sometimes forage in mixed-species flocks with any of the other four species of Australian corvids. Sometimes they are aggressive with little ravens if both are at a food source and drive them off, though not if the smaller species greatly outnumbers the larger.[34]

Australian ravens drink water frequently, up to ten times a day in hot weather. Birds have been observed dunking pieces of meat in water before eating them.[31]

Breeding

Australian ravens begin breeding once they are three years old.[30] Breeding season is from July to September.[35] Australian ravens generally nest in tall trees, never near to the ground as some species do. They occiasionally nest on buildings or telegraph poles.[24] Nests are generally large and untidy, consisting of a bowl or platform of sticks lined with grasses, barks, and feathers.[36] A clutch can comprise 3–6 eggs, though usually 4 or 5 are laid. Measuring 45 by 30 mm (1¾x1¼ in), eggs are pale green or bluish-green splotched with darker olive, brown and blackish markings.[35] Incubation of the eggs is done solely by the female over roughly 20 days. Only one brood is raised per year. Fledged by 45 days and staying with parents for about four months after that.

Rush Creek, SE Queensland, Australia

Parasites

A circovirus—given the name raven circovirus or RaCV—was isolated from an Australian raven suffering from feather lesions in 2006. It has affinities with canary circovirus (CaCV) and pigeon circovirus (PiCV). Its clinical significance is unknown.[37]

Relationship with humans

The Australian raven is frequently blamed for the loss of young lambs.[38] Scientific observation in the country's southeast showed that the killing of healthy lambs was rare but that sick animals were predisposed to being attacked.[39]

In indigenous religion

Main article: Crow (Australian Aboriginal mythology)

In Australian Aboriginal mythology, Crow is a trickster, culture hero and ancestral being. In the Kulin nation in central Victoria he was known as Waa (also Wahn or Waang) and was regarded as one of two moiety ancestors, the other being the more sombre eaglehawk Bunjil. Legends relating to Crow have been observed in various Aboriginal language groups and cultures across Australia.[40]

Notes

  1. ^ John Latham had described the south-seas raven in 1781, with loose throat feathers and being found in "the Friendly Isles" in the South Seas, but did not give it a binomial name.[6] The place is thought to be Tonga.[5] Gmelin gave it the name Corvus australis in the 13th edition of Systema naturae in 1788.[7]

References

  1. ^ Template:IUCN
  2. ^ a b Vigors, Nicholas Aylward; Horsfield, Thomas (1827). "A description of the Australian birds in the collection of the Linnean Society; with an attempt at arranging them according to their natural affinities". Trans. Linn. Soc. Lond. 15: 170–331 [261]. doi:10.1111/j.1095-8339.1826.tb00115.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Liddell, Henry George; Scott, Robert (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.{{cite book}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c d e f g Higgins 2006, p. 690.
  5. ^ a b c d e f g h Rowley, Ian (1970). "The Genus Corvus (Aves: Corvidae) in Australia". CSIRO Wildlife Research. 15 (1): 27–71. doi:10.1071/CWR9700027.
  6. ^ Latham, John (1781). A General Synopsis of Birds. Vol. 1. London, United Kingdom: Benj. White. p. 369.
  7. ^ Gmelin, Johann Friedrich (1788). Systema naturae per regna tria naturae :secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis /Caroli a Linné. Leipzig, Germany: Impensis Georg. Emanuel. Beer. p. 365.
  8. ^ Gould, John (1865). Handbook to The birds of Australia. London, United Kingdom: self. p. 475.
  9. ^ Ogilvie-Grant, William Robert (1912). "The Crows of Australia". Emu. 12 (1): 44–45. doi:10.1071/MU912044.
  10. ^ Mathews, Gregory M. (1912). "A Reference-List to the Birds of Australia". Novitates Zoologicae. 18: 171–455 [442].
  11. ^ Mathews, Gregory M. (1911). "Alterations in the nomenclature of "Handbook of the Birds of Australia"". Emu. 10: 317–26. doi:10.1071/MU910317.
  12. ^ a b Australian Museum Online. "Crows and Ravens". Archived from the original on 1 September 2007. Retrieved 12 August 2007. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  13. ^ Haring, Elisabeth; Däubl, Barbara; Pinsker, Wilhelm; Kryukov, Alexey; Gamauf, Anita (2012). "Genetic divergences and intraspecific variation in corvids of the genus Corvus (Aves: Passeriformes: Corvidae) – a first survey based on museum specimens" (PDF). Journal of Zoological Systematics and Evolutionary Research. 50 (3): 230–46. doi:10.1111/j.1439-0469.2012.00664.x.
  14. ^ Jønsson, Knud A.; Fabre, Pierre-Henri; Irestedt, Martin (2012). "Brains, tools, innovation and biogeography in crows and ravens". BMC Evolutionary Biology. 12. doi:10.1186/1471-2148-12-72.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  15. ^ Rowley, Ian (1973). "The Comparative Ecology of Australian Corvids. VI. Why five species?". CSIRO Wildlife Research. 18 (1): 157–69. doi:10.1071/CWR9730157.
  16. ^ Alexander, W.B. (1933). "Popular Names for Australian Birds" (PDF). Emu. 33 (2): 110–11. doi:10.1071/MU933110.
  17. ^ Troy, Jakelin (1993). The Sydney language. Canberra, ACT: self-published. p. 53. ISBN 0-646-11015-2.
  18. ^ a b c d e f Higgins 2006, p. 692.
  19. ^ Higgins 2006, p. 714.
  20. ^ a b c d Higgins 2006, p. 691.
  21. ^ Higgins 2006, p. 693.
  22. ^ a b c Higgins 2006, p. 694.
  23. ^ a b Birds in Backyards. "Australian Raven". Retrieved 12 August 2007.
  24. ^ a b c Higgins 2006, p. 696.
  25. ^ a b c Higgins 2006, p. 697.
  26. ^ "Birds of Rottnest Island". Rottnest Island Authority. Retrieved 25 November 2011.
  27. ^ Higgins 2006, p. 695.
  28. ^ a b Higgins 2006, p. 698.
  29. ^ a b Higgins 2006, p. 699.
  30. ^ a b c Rowley, Ian (1971). "Movements and longevity of ravens in south-eastern Australia". CSIRO Wildlife Research. 16 (1): 49–72. doi:10.1071/CWR9710049.
  31. ^ a b c d e Rowley, Ian (1973). "The Comparative Ecology of Australian Corvids. II. Social organization and behaviour". CSIRO Wildlife Research. 18 (1): 25–65. doi:10.1071/CWR9730025.
  32. ^ a b Rowley, Ian; Vestjens, W.J.M. (1973). "The Comparative Ecology of Australian Corvids. V. Food". CSIRO Wildlife Research. 18 (1): 131–55. doi:10.1071/CWR9730131.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  33. ^ Richardson, KC (1988). (abstract) "Are Australian corvids nectarivorous?". Emu. 88 (2): 122–23. doi:10.1071/MU9880122. Retrieved 14 Aug 2007. {{cite journal}}: Check |url= value (help)
  34. ^ Higgins 2006, p. 700.
  35. ^ a b Beruldsen, Gordon (2003). Australian Birds: Their Nests and Eggs. Kenmore Hills, Queensland: self. p. 384. ISBN 0-646-42798-9.
  36. ^ "Birds in Backyards".
  37. ^ Stewart, Meredith E.; Perry, Ross; Raidal, Shane R. (2006). "Identification of a novel circovirus in Australian ravens (Corvus coronoides) with feather disease". Avian Pathology. 35 (2): 86–92. doi:10.1080/03079450600597345.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  38. ^ Temby, Ian. "Predatory Birds". Archived from the original on 17 September 2007. Retrieved 12 August 2007. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help) [dead link]
  39. ^ Rowley, Ian (1969). "An evaluation of predation by 'crows' on young lambs". CSIRO Wildlife Research. 14 (2): 153–79. doi:10.1071/CWR9690153.
  40. ^ Mudrooroo (1994). Aboriginal mythology: An A-Z spanning the history of the Australian Aboriginal people from the earliest legends to the present day. London, United Kingdom: Thorsons. pp. 35–36. ISBN 978-1-85538-306-7.

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