The Torresian crow (''Corvus orru''), also called the Australian crow or Papuan crow, is a
passerine
A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by th ...
bird in the
crow family
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. In colloquial English, they are known as the crow family or corvids. Currently, ...
native to the north and west of
Australia and nearby islands in
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
and
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
. The species has a black plumage, beak and mouth with white
iris
Iris most often refers to:
*Iris (anatomy), part of the eye
*Iris (mythology), a Greek goddess
* ''Iris'' (plant), a genus of flowering plants
* Iris (color), an ambiguous color term
Iris or IRIS may also refer to:
Arts and media
Fictional ent ...
es. The base of the feathers on the head and neck are white. The Torresian crow is slightly larger with a more robust bill than the
morphologically similar
little crow.
Taxonomy
![Torresian Crow 2](https://upload.wikimedia.org/wikipedia/commons/1/1f/Torresian_Crow_2.jpg)
The Torresian crow was described by the French ornithologist
Charles Lucien Bonaparte in 1850.
The origin of the
specific epithet ''orru'' is not known but may be derived from a Papuan name.
There are three
subspecies:
* ''C. o. latirostris''
Meyer, AB, 1884 – east
Lesser Sunda Islands
* ''C. o. orru'' Bonaparte, 1850 –
Maluku Islands
The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located ...
, New Guinea,
D'Entrecasteaux Islands. and
Louisiade Archipelago
The Louisiade Archipelago is a string of ten larger volcanic islands frequently fringed by coral reefs, and 90 smaller coral islands in Papua New Guinea.
It is located 200 km southeast of New Guinea, stretching over more than and spread ...
* ''C. o. cecilae''
Mathews, 1912 – west, central and northern Australia
The
Bismarck crow
The Bismarck crow (''Corvus insularis'') is a species of crow found in the Bismarck Archipelago. It was considered by many authorities to be a subspecies of the Torresian crow
The Torresian crow (''Corvus orru''), also called the Australian cro ...
(''Corvus insularis'') on the
Bismarck Archipelago was formerly considered a subspecies.
[ In Central Australia southwest of Alice Springs, the ]Pitjantjatjara
The Pitjantjatjara (; or ) are an Aboriginal people of the Central Australian desert near Uluru. They are closely related to the Yankunytjatjara and Ngaanyatjarra and their languages are, to a large extent, mutually intelligible (all are va ...
term for race ''ceciliae'' is ''kaanka''. The term ''wati kaanka'' refers to a light-fingered man or someone who hangs around suspiciously.
Description
The Torresian crow is a large corvid
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. In colloquial English, they are known as the crow family or corvids. Currently, ...
, about the same size (48–53 cm in length) as the Eurasian carrion crow
The carrion crow (''Corvus corone'') is a passerine bird of the family Corvidae and the genus ''Corvus'' which is native to western Europe and the eastern Palearctic.
Taxonomy and systematics
The carrion crow was one of the many species or ...
but with a more robust bill and slightly longer legs. The plumage of the Torresian Crow is glossy black on the back and dull black on the breast with inconspicuous throat hackles. Its tail is broad and has a distinctive square-shaped tip. Its bill is dark grey and about the same length as the head. The legs and feet are a similar dark grey color with pink foot soles. The Torresian crow has the typical white iris of the other Australasia
Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...
n ''Corvus
''Corvus'' is a widely distributed genus of medium-sized to large birds in the family Corvidae. It includes species commonly known as crows, ravens and rooks. The species commonly encountered in Europe are the carrion crow, the hooded crow ...
'' species with a fine, blue eye-ring. However, it can be distinguished from most except the little crow by the base of the head and neck feathers being white. The white feather bases are revealed when ruffled. Birds of this species characteristically shuffle their wings after alighting. Sexes are identical in their appearance; however, juveniles lack glossy dorsal feathers and have blue eyes, rather than white, up to about nine months of age.
The Torresian crow is not to be confused with the Australian raven
The Australian raven (''Corvus coronoides'') is a passerine bird in the genus '' Corvus'' native to much of southern and northeastern Australia. Measuring in length, it has all-black plumage, beak and mouth, as well as strong grey-black legs an ...
which has an almost identical appearance. Despite their visual similarities, the Australian raven and crow have very different and unique calls.
Distribution and habitat
The Torresian crow has an extensive distribution across Australia, Papua New Guinea in particular the Bismarck Archipelago and some islands in Indonesia, in particular the Moluccas
The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located ...
. The range of the mainland Australian race
Race, RACE or "The Race" may refer to:
* Race (biology), an informal taxonomic classification within a species, generally within a sub-species
* Race (human categorization), classification of humans into groups based on physical traits, and/or s ...
''C. orru ceciliae'' extends from the tropical north of Australia to as far south as Forster on the east coast of New South Wales
)
, nickname =
, image_map = New South Wales in Australia.svg
, map_caption = Location of New South Wales in AustraliaCoordinates:
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, es ...
and to between Geraldton
Geraldton ( Wajarri: ''Jambinu'', Wilunyu: ''Jambinbirri'') is a coastal city in the Mid West region of the Australian state of Western Australia, north of the state capital, Perth.
At June 2018, Geraldton had an urban population of 37,648. ...
and Norseman in South Western Australia.
The Torresian crow occupies almost any habitat within its geographic range where there is a permanent source of water. The species is common in habitats such as tropical rainforests
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equa ...
, eucalyptus
''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as e ...
woodland, open scrub, beaches
A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shel ...
, swamps, offshore islands. The Torresian crow is also well adapted to fringe habitats including farmland, towns and cities. On farms in much of Northern Australia, they are the most numerous bird species and are considered a pest by farmers, as they damage crops such as sweetcorn, peanut
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics, important to both small and ...
s, wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
and many kinds of fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
. Torresian crows are common in urban landscapes and many cities and towns in Australia support large populations. In the arid zones of central Australia, the species is sparsely distributed and confined to areas with permanent water.
Two other races occur on various islands to the north: ''C. orru orru'' in Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
and the Moluccas
The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located ...
), and ''C. orru latirostris'' on Tanimbar and Babar Islands.
Ecology
Expansion of the Torresian crow population in Australia
The Torresian crow, similarly to many corvids, is an opportunistic species and has adapted to a broad range of habitats. The population size of Torresian crows in Australia is increasing, possibly owing to the expansion of agricultural activity in arid areas, as well as increased urbanization
Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...
. Studies on the distribution of Torresian Crows across Australia, between 1993 and 2004, have shown that the geographic range of the species has expanded into highly urbanized regions including many of Australia's largest cities, as well as further south into arid areas of central Australia. The continued urban growth of Australia in the past decades has resulted in large areas of natural subtropical and eucalypt sclerophyll
Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short internodes (the distance between leaves along the stem) and leaf orientation which is parallel or oblique to direct ...
forest to be replaced by suburbs and parkland, especially in the regions surrounding major cities. This increased urbanisation of land has been associated with the observed proliferation of Torresian crows. Over a long-term study in urban to suburban areas of South-East Queensland, the abundance of Torresian crows was observed to have increased by about 40%. The density of the species in Brisbane has become such that the noise resulting from the congregation of large numbers of individuals in communal roosting sites located in urban areas, has become a source of complaints by local residents.
The population of Torresian crows has also expanded in rural areas across Australia. Increased development of land for agricultural activities is likely to be a significant factor influencing the rising population size of the species outside urban areas. In rural areas, Torresian crows have been found to congregate in agricultural environments and form large flocks. Since the species is reliant on a permanent source of water for their survival, large groups of Torresian crows are most commonly observed on cultivated land in the tropics and in the East of the country where annual rainfall is relatively higher. Whilst the distribution of Torresian crows has expanded further across all of Australia, the density of the species in arid areas remains low due to a lack of sustainable water sources. In the arid centre, the species is primarily confined to localised areas where the amount of water in streams and waterholes is enhanced by high runoff in surrounding regions. However, the development of irrigation systems and wells by the cattle and farming industry may have provided the species with sufficiently stable sources of water to allow them to establish in areas that were previously untenable.
Edge species
The expansion of corvid species populations in urban areas worldwide is due to their ability to exploit edge habitats. This has allowed corvids including the Torresian crow to take advantage of urban growth by exploiting the associated increase in anthropogenic food resources and by dominating the resulting urban habitat, reducing the competition imposed by other species.
One of the reasons the Torresian crow is able to take advantage of increased urbanisation is its diet; a significant proportion of the diet of the species consists of carrion, which is abundant in urban environments due to road kill. Anthropogenic waste also provides Torresian crows with a plentiful source of food requiring minimal foraging. Furthermore, food resources of the Torresian crow may be indirectly supplemented by the modification of land coverage, where native forests are replaced by lawns and parkland that are rich in invertebrates which also represent a significant part of the species' diet. The abundance of food means that little intra-specific aggression is observed since resources are not economically defensible. Finally, the large size of Torresian crows allows them to dominate food resources and hence experience little competition
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indiv ...
from other smaller urban bird species.
A second aspect allowing the Torresian crow to expand into urban areas is its breeding requirements. The species only requires very minimal breeding space making it well adapted to living in a dense urban landscape. This allows the formation of large communal roosts resulting in a high population density. Therefore, the carrying capacity of urban habitats for Torresian crows is comparatively much higher than that of rural areas where resources are more limited.
The urban sprawl
Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city." Urban sprawl has been described as the unrestricted growt ...
in Australia is continually creating new habitat for the species and is likely to be a strong contributing factor in the observed increase in population size. Even relatively small urban developments on previously untouched land can represent significant increases in breeding space for Torresian crows to colonize, given the large carrying capacity of these habitats.
Behaviour
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. Torresian crows are large and aggressive birds, with females displaying the more aggressive behaviour and dominating most other species except large birds of prey
Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition to speed and strength, these predat ...
and the Australian magpie
The Australian magpie (''Gymnorhina tibicen'') is a black and white passerine bird native to Australia and southern New Guinea. Although once considered to be three separate species, it is now considered to be one, with nine recognised su ...
. They have been observed to attack larger birds of prey, particularly wedge-tailed eagle
The wedge-tailed eagle (''Aquila audax'') is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. Adults of this species have lon ...
s and most owl
Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...
species in defence of their nest or territory. Smaller birds will therefore attack crows in defence of their nests, with willie wagtail
The willy (or willie) wagtail (''Rhipidura leucophrys'') is a passerine bird native to Australia, New Guinea, the Solomon Islands, the Bismarck Archipelago, and Eastern Indonesia. It is a common and familiar bird throughout much of its range, ...
s and pied butcherbirds being notable examples. Noisy miner
The noisy miner (''Manorina melanocephala'') is a bird in the honeyeater family, Meliphagidae, and is endemic to eastern and southeastern Australia. This miner is a grey bird, with a black head, orange-yellow beak and feet, a distinctive yellow ...
s and Australian magpie
The Australian magpie (''Gymnorhina tibicen'') is a black and white passerine bird native to Australia and southern New Guinea. Although once considered to be three separate species, it is now considered to be one, with nine recognised su ...
s 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. 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
A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal.
In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
, with the nomadic flock sizes reducing significantly to only young and old crows. Each pair of crows returns to the same territory each year, but territories may be taken over by other pairs from year to year.[Chisholm, A H (1976). ''Complete Book of Australian Birds''. Reader's Digest Services. p. 581]
Diet
Torresian crows are omnivores and consume a wide range of foods. Their diet varies significantly between habitats with birds living in urban environments relying to a greater extent on anthropogenically related food sources compared to those living in natural habitats. Outside urbanised areas, the diet of Torresian crows primarily consists of invertebrates, berries and carrion. Birds of this species have also been observed to take stranded fish on the seashore, roadkill, fruit, grain, smaller birds and rodents. In Northern Australia Torresian crows have developed a remarkable technique to kill and eat the introduced poisonous cane toad
The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...
without ingesting the poison it secretes from its skin and poison glands on either side of its head, by flipping it onto its back and delivering a lethal blow with its powerful bill. The crows only feed on the intestines and part of the thighs of the toad, thus avoiding the poison. This predation and consumption technique is culturally
Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ...
transmitted amongst crows of the species.
''For further information on the adaptation of Torresian crows to cane toads see: Adaptations of Australian animals to cane toads''
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
Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera (of the tribe Eucalypteae) found across Australasia:
''Eucalyptus'', ''Corymbia'', ''Angophora'', '' Stockwellia'', ''Allosyn ...
, 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. 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 goanna
A goanna is any one of several species of lizards of the genus '' Varanus'' found in Australia and Southeast Asia.
Around 70 species of ''Varanus'' are known, 25 of which are found in Australia. This varied group of carnivorous reptiles ranges ...
s, snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...
s 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.
Voice
Their voice is quite different from the Australian raven: whilst the more standard loud penetrating Australian raven/crow call ''"Fark! Fark!"'' may occur there is often a more nasal, metallic clattering ''"uk-uk-uk-uk-uk"'' or sometimes an ''"ok-ok-ok-ok"'' or ''"Ar-ar-argh"'', sometimes with an upward inflection, somewhat like a cat meow. This may be following the more standard call or may be delivered in isolation.
References
Further reading
*
External links
xeno-canto: Sound recordings of the Torresian crow
{{Taxonbar, from=Q1584645
Corvus
Birds of Australia
Birds of the Maluku Islands
Birds of New Guinea
Birds described in 1850
Taxa named by Charles Lucien Bonaparte