Torresian crow

"Australian crow" redirects here. For the butterfly, see Euploea core.
Torresian crow
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Corvus
Species: C. orru
Binomial name
Corvus orru
Bonaparte, 1850

The Torresian crow (Corvus orru), also called the Australian crow or Papuan crow, is a passerine bird in the crow family native to the north and west of Australia and nearby islands in Indonesia and Papua New Guinea. It has all-black plumage, beak and mouth with white irises. Like those of the other species of crow native to Australia, the little crow, its black feathers have white bases.

Taxonomy

The Torresian crow was described by the French ornithologist Charles Lucien Bonaparte in 1850.[2][3] The origin of the specific epithet orru is not known but may be derived from a Papuan name.[4]

There are three subspecies:[5]

The Bismarck crow (Corvus insularis) on the Bismarck Archipelago was formerly considered a subspecies.[5][7] In Central Australia southwest of Alice Springs, the Pitjantjatjara term for race ceciliae is kaanka. The term wati kaanka refers to a light-fingered man or someone who hangs around suspiciously.[8]

Description

The Torresian crow is about the same size (48–53 cm in length)[9] as the Eurasian carrion crow but with a more robust bill and slightly longer legs. It has the typical white iris of the other Australasian Corvus species but can be distinguished from most (except the little crow) by the base of the head and neck feathers being snow white (revealed when blown by a strong wind). It also shuffles its wings after alighting.

Distribution and habitat

The range of the mainland Australian race C. orru ceciliae occupies the tropical north of Australia as far south as Brisbane on the east coast where the species seems to be adjusting well to a city life. Over much of this range, it is simple to distinguish from other species, as it is the only corvid found in northern Australia.

They occupy almost any habitat within their range, except the deserts of inland Australia, where they are replaced by the smaller Little crow. They can be found in habitats such as tropical rainforests, eucalyptus woodland, open scrub, beaches, swamps, offshore islands, farmland, towns and cities. On farms in much of Australia, they are the most numerous bird species and are considered a pest by farmers, as they damage crops such as corn, peanuts, wheat and many kinds of fruit.

Two other races occur on various islands to the north: C. orru orru (the nominate form from Papua New Guinea and the Moluccas), and C. orru latirostris of Tanimbar and Babar Islands.

The Australian crow is not to be confused with the Australian raven which has an almost identical appearance. Despite their visual similarities, the Australian raven and crow have very different and unique calls.

Behaviour

Torresian crows are large and aggressive birds, dominating most other species except large birds of prey and the Australian magpie. Between the months of January and August, large groups of crows congregate and roam nomadically across farmlands, forests and city suburbs. These groups consist of crows of all ages, however from September to December, many leave these flocks to breed in temporary territories, with the nomadic flock sizes reducing significantly to only young and old crows. Each pair of crows returns to the same territory each year, however territories may be taken over by other pairs from year to year.[10]

Like other corvids, Torresian crows are intelligent and adaptable and have been known to steal food from larger birds by working in teams, and to feed on poisonous prey without ingesting poison (see below) among other behaviours. They are also aggressive birds and will attack larger birds of prey, particularly wedge-tailed eagles and most owl species in defence of their nest or territory.[10] However unlike other birds, they mob larger birds at all times, not limiting mobbing behaviour to the breeding season. They have been known to kill smaller raptors such as barn owls and nankeen kestrels, and also other birds such as crested pigeons and ducks for no apparent reason. Smaller birds will therefore attack crows in defence of their nests, with willie wagtails and pied butcherbirds being notable examples. Noisy miners and Australian magpies are among the few birds that are successful in driving Torresian crows out of their territories, with the latter species being one of the smaller bird species that dominate and displace crows where they meet.[10]

Diet

A typical crow in that it will take just about anything. It has been seen taking stranded fish on the seashore, roadkill, human food scraps, fruit, grain, smaller birds, rodents and insects. Adaptable and intelligent like its North American, European, African and Asian relatives, in Australia it has learned how to kill and eat the introduced poisonous cane toad without ingesting the poison by flipping it onto its back and delivering a lethal blow with its powerful bill. It will also pick skin parasites off of the Australian water buffalo (a relationship that took around 150 years to develop).

Nesting

The main breeding period occurs from August to January, with most eggs being laid in September and October. The stick nest is built high in a tree, usually a eucalypt, however other locations such as power pylons and tall buildings are occasionally chosen. Two to four eggs are laid which the female incubates for roughly twenty days and then is assisted by the male in rearing the chicks for around forty days until they leave the nest.[10] Young Torresian crows then stay with their parents for several months after fledging, before joining the nomadic flock. Torresian crows aggressively defend their nest from goannas, snakes and birds of prey with aggressive dive-bombs. Dogs, cats and humans are also occasionally swooped in nest defence, however not nearly as aggressively as notorious species such as Australian magpies and masked lapwings.[10]

Voice

Quite different from the Australian raven. A nasal "uk-uk-uk-uk-uk" or sometimes an "ok-ok-ok-ok".

References

  1. ↑ BirdLife International (2012). "Corvus orru". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ Bonaparte, C.L. (1850). Conspectus Generum Avium (Volume 1) (in Latin). Lugduni Batavorum (Leiden): E.J. Brill. p. 385.
  3. ↑ Blake, E.R.; Vaurie, C. (1962). "Family Corvidae, Crows and Jays". In Mayr, E.; Greenway, J.C. Jnr. Check-list of birds of the world (Volume 15). Cambridge, Mass.: Museum of Comparative Zoology. p. 275.
  4. ↑ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 285. ISBN 978-1-4081-2501-4.
  5. 1 2 Gill, Frank; Donsker, David (eds.). "Crows, mudnesters & birds-of-paradise". World Bird List Version 6.1. International Ornithologists' Union. Retrieved 27 January 2016.
  6. ↑ Mathews G.M. (1912). "A reference-list to the birds of Australia". Novitates Zoologicae 18: 171–455 [442].
  7. ↑ Dutson, G.; Gregory, P.; Boles, W. (2011). "Bismarck Crow Corvus (orru) insularis warrants species status". Bulletin of the British Ornithologists' Club 131 (3): 204–206.
  8. ↑ Goddard, Cliff (1992). Pitjantjatjara/Yankunytjatjara To English Dictionary (2 ed.). Alice Springs, Northern Territory: Institute for Aboriginal Development. p. 26. ISBN 0-949659-64-9.
  9. ↑ Campbell, Iain; Woods, Sam; Leseberg, Nick. Birds of Australia: A Photographic Guide Princeton University Press, 2015. p.330
  10. 1 2 3 4 5 Chisholm, A H (1976). Complete Book of Australian Birds. Readers Digest Services. p. 581

Further reading

External links

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