Tiaras
| Tiaras | ||||||||||||
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Blue jay ( Cyanocitta stelleri frontalis ) in Yosemite National Park |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Cyanocitta stelleri | ||||||||||||
| ( Gmelin , 1788) |
The Steller ( Cyanocitta stelleri ) is an American songbird from the family of corvids (Corvidae). The black and blue colored jays are about the size of a dove with a length of 30–34 cm and are characterized by their pronounced head of feathers. The distribution area of the species extends from Alaska along the Cordilleras southwards to Nicaragua , with the more southern forms being smaller and lighter in color. Loose coniferous and mixed forests form the preferred habitat of the diademed mower. The birds feed omnivorously on nuts , berries , insects and small vertebrates . The diademed jay builds its nest in tree tops. The clutch consists of two to six eggs from which the young hatch after about 16 days.
The first scientific description of the diademed mower comes from Johann Friedrich Gmelin from 1788 and is based on a specimen that Georg Wilhelm Steller collected on the Second Kamchatka Expedition. The closest relative of the species is the blue jay ( Cyanocitta cristata ), which inhabits eastern North America from the Rocky Mountains to the Atlantic. Both species probably separated around 5 million years ago in the late Miocene . From Alaska to Central America there are around 17 subspecies of Cyanocitta stelleri , which can be more or less easily differentiated from one another. With the exception of the population in El Salvador , the species is not considered threatened anywhere.
features
With a body length of around 30–34 cm, the diademed jay is roughly the same size, but at 98–142 g only a third to half as heavy as a city pigeon ( Columba livia ). There is a slight sexual dimorphism between males and females : on average, females are slightly smaller than males of the same subspecies, but there is a strong overlap in terms of dimensions. The hand wing becomes 132–157 mm long in females and 140–164 mm long in males. The tail of the species reaches a length of 122-147 (females) and 131-160 mm (males). Female tiaras reach beak lengths of 26–31 mm, males 26–32 mm. The barrel measures 38–48 mm in females and 41–50 mm in males.
The beak is longer and narrower and the hood is more pronounced than that of the blue jay . The plumage is black on the head, throat, chest and upper back, and dark blue on the belly, trunk, tail and wings. There are white stripes on the forehead, some birds have a white stripe above the eyes. The wings of the hand and the tail have darker horizontal stripes. The appearance of the bird varies in the area of distribution. While the head is brown-black in the north, it becomes more and more bluish the further south you go.
The call of the tiaras includes a series of rattling and guttural sounds. The warning call is a rough, nasal “wah”. The bird also mimics the red-tailed buzzard's call to drive other birds away from feeding grounds.
Occurrence
The diademed jay inhabits wooded mountainsides and light wooded areas with pine trees in western America from Alaska to California and parts of Central America. In winter the bird can also be found in the lowlands.
behavior
The diademed jay looks for seeds, nuts, berries, invertebrates, eggs and nestlings on the ground or in trees. Vegetable food, such as acorns and seeds from conifers, is collected for the cold season. Like other corvids, it can hold food with its foot and hammer it with its beak. The beak is also used for digging and peeling off loose bark. The bird lives in pairs and families; if there is a good source of food, larger flocks of more than ten birds will gather.
Reproduction
Two to six eggs are laid in a bowl-shaped nest made of twigs, leaves, moss and mud on a horizontal branch near the trunk. These are colored a pale green-blue, with brown or olive-colored spots, and are predominantly incubated by the female for 17 to 18 days. The young birds fledge at three weeks. Where the circulation area overlaps with that of the bluejay, such as in Colorado , are hybrid forms observed.
Trivia
- The bird is one of the animals whose scientific name was named after the German naturalist Georg Wilhelm Steller .
- The diademed jay has been the heraldic bird of the Canadian province of British Columbia since 1987 .
literature
- Colin Harrison & Alan Greensmith: Birds. Dorling Kindersley Limited, London 1993, 2000, ISBN 3-8310-0785-3
- Bryan Richard: Birds. Parragon, Bath, ISBN 1-4054-5506-3
Web links
- Erick Greene, William Davison, Vincent R. Muehter: Steller's Jay (Cyanocitta stelleri) . In: Poole, A .; Gill, F. (Ed.): The Birds of North America Online . 1998, doi : 10.2173 / bna.343 .
- J. Marzluff: Steller's Jay (Cyanocitta stelleri) . In: Handbook of the Birds of the World Alive . Lynx Edicions, Barcelona 2016.
Individual evidence
- ↑ Greene et al. 1998, appendix.