Social crow
| Social crow | ||||||||||||
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Social crow |
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| Corvus mellori | ||||||||||||
| Mathews , 1912 |
The society crow ( Corvus mellori ) is a bird from the genus of ravens and crows ( Corvus ). It occurs exclusively in the south of Australia and some islands off the south Australian coast. Compared to other Corvus species found in this region, it is more sociable. Outside the breeding season, small flocks roam a larger area and they occasionally breed in small, loose colonies when suitable nesting trees are scarce.
Society crows utilize a wide range of food sources and are very adaptable in their habitat requirements.
The population of the crowded crow was classified in the IUCN's Red List of Endangered Species in 2016 as “ Least Concern (LC) ” = “not endangered”. No subspecies are distinguished.
features
Build and color
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Between the sexes society Crow is neither in the plumage coloration still in Build a dimorphism , the same applies to young and adult birds. It reaches a body length of 48 to 52 cm. The beak is 55.6–67.7 mm long. The society crow has a wing length of 329–341.7 mm, its tail measures 185–193 mm. The weight is between 421 and 600 g. It is thus only slightly smaller than the New Holland crow , the most widespread Corvus species in Australia .
The plumage of the society crow is uniformly black. The plumage on the head, neck, upper side of the body, breast, flanks and the plumage of the under tail-coverts shine black. The shimmer ranges from a metallic green on the ear covers to a blue-violet shimmer on the other parts of the body. The intensity of the shimmer strongly depends on the incidence of light. The underside of the body is matt black. The feathers on the chin and throat are comparatively long and reach the chest. They shimmer blue-violet to greenish in good light conditions.
The feathers have a pale gray feather base, the feathers are black only from the middle. In living birds, this feather base is visible when strong winds blow the feathers apart.
The beak is black, the rear third of the upper beak including the nostrils is covered by bristle feathers. In adult birds, the iris is whitish with a light blue inner ring. The legs and feet are black.
Fledglings
Young birds are slightly smaller than the adult birds. Their beak is even shorter. The plumage is not as shiny as in the adult birds and looks a bit brownish. Their beak is still dark gray, the iris is blue-gray.
Possible confusion
In Australia, come Corvus TYPES Salvadorikrähe , Neuhollandkrähe , Tasmankrähe and Bennett Crow ago that are difficult to distinguish in field observations by the company crow. The elongated feathers on the chin and throat, as they are typical of the social crows, can also be found in the New Holland crows and the Tasman crows. The most reliable distinguishing feature is reputation.
Distribution area and habitat
Distribution area
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The range of the common crow is the southeast of the Australian mainland as well as the King Island , a Tasmanian island with an area of 1,098 km² at the western end of the Bass Strait (Bass Strait) between Tasmania and Australia. In Australia, it populates most of the Australian state of New South Wales . In South Australia it occurs south of 31 ° south latitude, but is absent in the southwest of this state.
habitat
The social crows inhabit a number of very different habitats. Outside of the breeding season, it can be found in grasslands and pastures. During the breeding season, however, it is dependent on tall trees as a nesting site. It can then be found in the remains of dry hardwood forests or in small groves, but looks for food in open terrain. It also occurs in urban areas and is mainly found in urban areas that have a very plentiful supply of food.
Breeding pairs only occupy territories for about three months As soon as the young birds have fledged, the family association joins troops consisting of young birds and non-breeding adult community crows that roam a larger area. The migratory movements of these troops have not yet been very well studied. However, young birds move through a larger area in the first and second year of life.
Way of life
The society crow lives mostly in small to large groups. Troops of more than a hundred individuals are observed regularly. They are only observed solitary or in pairs during the breeding season. It is occasionally associated with the New Holland crow and the Bennett crow.
food
The society crow is an opportunistic omnivore. However, it covers a large part of its nutritional needs with insects. It also eats small vertebrates, including smaller species of birds, eggs and nestlings. Carrion also plays a role in their diet, although this plays a lesser role in them than in the New Holland crow. It also eats seeds and fruits. The food composition varies seasonally due to the different availability.
Reproduction
The breeding season falls from May to early December. Society crows nest either as a single breeding pair or in loose, small breeding colonies. In the breeding colonies, the nests are often very close to one another. There are then, for example, 15 occupied nests on a 1.25 hectare property. Such breeding colonies occur mainly in regions where suitable nesting trees are rare. In these breeding colonies, too, a breeding pair defends a small area around the nest. The food is sought outside of this area. Society crows defend this territory not only against conspecifics, but also against predators such as wedge-tailed eagles , which among other things steal the nestlings of this species.
The nest is built from branches and twigs, the actual nesting trough is covered with grass, bark, feathers, wool and hair, but also rubbish such as paper or items of clothing. Both parent birds are involved in building the nest. More often, nests of the previous breeding season are used again. In these cases, the birds usually remove the padding from the nesting trough and then add the branches and twigs to the nest. The interior of the nest is then laid out again with new materials.
There are usually two to three days between the start of nest building and the laying of the first egg. The full clutch consists of one to six eggs. The typical clutch size varies between three and five eggs. The female lays the eggs a day or two apart. A laying interval of two days is typical, especially after the second egg is laid. If the clutch is lost, a replacement clutch is often laid, as is the case up to four weeks after the clutch has been lost. In contrast, no second brood is raised in a breeding season.
The female breeds alone. The breeding season is 19 to 20 days. The nestlings hatch asynchronously. They weigh around 15 grams when they hatch, are still blind and bare apart from a few downs. By contrast, the nestlings are fully feathered on their 44th day of life. Both parent birds feed the offspring. However, they are huddled by the female alone. It is not yet known when the young birds are independent. When they are around three months old, they are still provided with food by their parent birds.
Life expectancy
Society crows are long-lived birds. A crowd crow that was ringed as an adult bird was found 10 years and 8 months later. Of the young birds, however, around 50 percent die in the first year of life.
literature
- PJ Higgins, JM Peter and SJ Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . Oxford University Press, Melbourne 2006, ISBN 978-0-195-55884-5 .
Web links
- Videos, photos and sound recordings of Corvus mellori in the Internet Bird Collection
Individual evidence
- ↑ Corvus mellori in the endangered Red List species the IUCN 2017. Posted by: BirdLife International, 2016. Accessed January 14, 2018th
- ↑ a b Handbook of the Birds of the World on Society Crows , accessed on May 15, 2017
- ^ A b Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 727.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 729.
- ↑ a b c d Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 730.
- ^ A b Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 731.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 732.
- ^ A b Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 740.
- ^ A b Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 736.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 738.
- ↑ a b c Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 741.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 733.