Tasman crow
| Tasman crow | ||||||||||||
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Tasman crow |
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| Scientific name | ||||||||||||
| Corvus tasmanicus | ||||||||||||
| Mathews , 1912 |
The tasmank crow ( Corvus tasmanicus ) is a bird belonging to the genus of ravens and crows ( Corvus ). It occurs exclusively in Australia and Tasmania as well as some of the islands off the coast. It is the largest and heaviest species of corvids in Australia . Tasmanian crows utilize a wide variety of food sources and are very adaptable. The IUCN classifies its stock situation as safe ( least concern ).
features
Build and color
Between the sexes of Tasmankrähe 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 50 to 53 cm. The beak is 63.4 to 66.1 mm long. The tasmank crow has a wing length of 352 to 360 mm, its tail measures 195 to 201 mm. The weight is between 639 and 680 g. This makes it slightly larger than the New Holland crow , the most widespread Corvus species in Australia .
The plumage of the Tasman 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 slightly elongated.
The feathers have a pale gray to medium gray feather base, the feathers are black only from the middle. In live birds, however, the lighter 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 society Crow , Neuhollandkrähe , Salvadorikrähe and Bennett Crow ago that are difficult to distinguish in field observations of the Tasmankrähe. However, elongated neck feathers, as are typical of the Tasmanian crow, only occur in the society crows and the New Holland crows. The most reliable distinguishing feature is reputation.
Distribution area and habitat
The range of the tasmin crow is limited to Tasmania and the southeast of Australia. In Australia, it occurs almost only in the states of New South Wales and Victoria. The distribution area there is disjoint. The distribution area in New South Wales is limited to the highlands of the New England region . In Victoria, the tasmank crow occurs in the Gippsland , the Otway Ranges and in the region around the Grampians National Park . In Tasmania, on the other hand, it is possibly the most widespread bird species.
The migratory behavior of the tasmank crow has not yet been conclusively investigated. Basically, it is assumed that, similar to the New Holland crow, a couple occupies a territory all year round. In contrast, not yet sexually mature birds and adult, non-breeding birds roam a larger area. The Bass Strait , a strait that separates Tasmania from mainland Australia, is regularly crossed by them. Accordingly, they can also be found on all islands in this strait.
The tasmank crow's habitat is predominantly hard deciduous forests, which are dominated by eucalyptus trees. In mainland Australia, they can be found predominantly in moist hardwood forests, which have more than 800 millimeters of annual rainfall. In contrast, they colonize a number of very different habitats in Tasmania. Among other things, they are often found in coastal regions and on the offshore islands with breeding colonies of sea birds. They are also found on farmland and rubbish tips, and can also be seen in parks and gardens in some coastal cities. As scavengers, they are also often seen along roadsides.
food
The tasmank crow is an opportunistic omnivore and therefore uses a very wide range of food. It covers most of its nutritional needs with insects and other invertebrates. There are also small vertebrates such as reptiles. It also eats small species of birds as well as the nestlings and eggs of various bird species. For example, it is a major predator of the chicken goose offspring . Carrion also plays a huge role in their diet. It also eats plant-based foods. These are mostly seeds and occasionally also fruits.
They usually look for food solitary or in pairs. At particularly rich sources of food, such as on rubbish tips, on large carcasses or during an insect plague, a large number of tasmank crows can also gather. It is then occasionally associated with other Australian Corvus species. In Tasmania it is during foraging sometimes with thick-billed Gulls , Silver head seagull and Tasmanwürgerkrähen ( Strepera fuliginosa socialized).
Reproduction
The reproductive biology of the tasmin crow has not yet been conclusively investigated. What is certain, however, is that the Tasmanian crow breeds a little later on Tasmania than on mainland Australia. In the Australian state of New South Wales, tasmank crows breed from July to September, in the Australian state of Victoria from July to October.
The nest is in the forks of trees, usually very high up in the treetop. It is a loose nest made of branches and twigs, the nesting trough is covered with grass, leaves, bark, feathers, fur and wool. Tasmanian crows that breed in Tasmania have a clutch size of four or five eggs. The laying interval is one to two days. Only females have a brood spot , so it can be assumed that only they incubate the clutch. Males always bring food to the breeding female. The breeding and nestling times are not yet known.
Life expectancy
Up to now there are only a few ringing data available for the tasmank crow, so that it is hardly possible to make any statements about how old tasmank crows can get. A tasmank crow ringed as an adult bird was recaptured four years and 7 months later, so that life expectancy is at least six years.
Tasmanian crow and people
In Australia and Tasmania, the tasmank crow is predominantly a harmful bird that attacks sheep and poultry and causes damage to orchards, vegetable and grain fields. Detailed investigations have not been able to confirm these assessments: The tasmank crow eats numerous agricultural pests and the benefits far outweigh the damage it causes. In Tasmania, tasmin crows are still being poisoned and occasionally shot in large numbers every year.
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 tasmanicus in the Internet Bird Collection
Individual evidence
- ↑ a b c Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 717.
- ↑ Handbook of the Birds of the World on the New Holland Crow , accessed on May 11, 2017
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 726.
- ^ 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. 719.
- ^ A b Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 720.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 718.
- ^ PJ Higgins (ed.): Handbook of Australian, New Zealand & Antarctic Bird. Volume 1. Ratites to Ducks. Oxford University Press, Oxford 1990, ISBN 0-19-553068-3 . P. 1199
- ↑ a b c Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 721.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 724.
- ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 725.