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Corvus coronoides

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Title: Corvus coronoides  
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Corvus coronoides

Australian Raven
Australian National Botanic Gardens, Canberra, ACT
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Corvus
Species: C. coronoides
Binomial name
Corvus coronoides
Vigors & Horsfield, 1827
Subspecies
C. c. coronoides
C. c. perplexus

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 a white iris. It is distinguished by its prominent throat hackles and grey bases of its black feathers. 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. 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;[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]

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.[5] Preliminary 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 is a suggestion the Little Raven may be nested within the Australian Raven, though more genetic work needs to be done.[6] 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.[7]

Alternate names sometimes seen include Southern Raven, Southern Crow, White-eyed Crow and Kelly.[4] It was called wugan by the local Eora and Darug inhabitants of the Sydney basin.[8]


Two subspecies are recognised:

  • C. c. coronoides, the nominate subspecies, is found across most of eastern Australia.[4]
  • C. c. perplexus 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 has a slightly lower-pitched call than that of the eastern subspecies.[9] Intermediate birds are found in the Eyre Peninsula, Gawler Ranges and vicinity of Lake Eyre in South Australia.[4]

Description


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 and a white iris. 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.[10] 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.[9] 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.[10] 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.[9] 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 raven species are more heavily set with a broader chest than the two crow species, with the Forest Raven the stockiest of all.[11]

Juveniles resemble adults, but have dark eyes, shorter throat hackles, and sometimes have a pink fleshy gape.[12] Their plumage is more ruffled and softer in appearance and lacks the glossy highlights, and their bill is shorter.[10]

The territorial call of the Australian Raven is a slow, high ah-ah-aaaah with the last note drawn out. It will use this call to communicate with other Australian Ravens in the area.[5] The five Australian species are very difficult to tell apart, with the call being the easiest way to do so.[4] It co-occurs with the Forest Raven in northeastern New South Wales from Port Stephens northwards, and with the Little Raven over much of central New South Wales, Victoria and into South Australia.[9]

Distribution and habitat

The Australian Raven is common throughout south-eastern Australia,[12] 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,[13] 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.[14] It is found on some offshore islands such as Rottnest Island.[15] and Kangaroo Island.[14] 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, it is restricted to more forested areas while the latter species prefers more open areas.[16]

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.[9]

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.[17] 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.[18]

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.[17]

Diet

Food consists of carrion, insects, seeds, fruit, small reptiles, nestlings and eggs. The preference ratio is 34% carrion, 42% invertebrates and 24% plant material. Food is taken mainly from the ground but will occasionally feed in trees. Ravens have adapted well to eating rubbish and scraps in urban areas, such as school playgrounds. In one isolated study they were observed feeding on nectar from eucalypt flowers.[19]

Reproduction

Breeding season is from July to September.[20] Ravens always nest in tall trees, never near to the ground as some species do. Nests are generally large and untidy, consisting of a bowl or platform of sticks lined with grasses, barks, and feathers.[21] 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.[20] 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.

File:Australian Raven charleville.ogg

Relationship with humans

The Australian Raven is frequently blamed for the loss of young lambs.[22] 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.[23]

References

Cited text

External links

  • An Australian Raven call (two birds)
  • Australian Raven videos, photos & sounds on the Internet Bird Collection
  • Australian Raven series (photos)
  • Australian Raven (photo)
  • A photo of Australian Ravens feeding on carrion
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