Green arborvitae
| Green arborvitae | ||||||||||||
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Green arborebird, Lamington National Park , Queensland |
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| Ailuroedus crassirostris | ||||||||||||
| ( Paykull , 1815) |
The Green Catbird ( Ailuroedus crassirostris ) is a kind from the family of Bowerbirds (Ptilonorhynchidae) and is a member of the avifauna of Australia . Compared to the closely related gardener birds found in New Guinea , this type of bower bird has been well researched due to its distribution area in Australia. Despite the comparatively large distribution area, no subspecies are distinguished for this species.
With a body length of up to 32 centimeters, the green arborebird is one of the larger representatives in the bowerbird family. It is one of the species whose courtship behavior does not include the construction of an arbor by the male. They are monogamous and have a relationship of several years. Both sexes defend a territory all year round .
Green arborebirds are very long-lived and take several years to reach sexual maturity. From ringing data it is known that they can reach an age of at least 13 years. According to the IUCN, their stock situation is classified as safe ( least concern ).
features
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The males of the green arboreal bird reach a body length of up to 32 centimeters, of which 11.1 to 13.9 centimeters are on the tail. The females stay a little smaller with a height of up to 30 centimeters. They account for 10.8 to 12.7 centimeters on the tail plumage. The beak length of the male is 3.1 to 3.8 centimeters, that of the females is between 3 and 3.69 centimeters. Males weigh between 167 and 289 grams, females remain slightly lighter with a weight between 169 and 211 grams. Apart from the difference in size, there is no noticeable gender dimorphism .
Green arborebirds have a green upper body. On the crown of the head, the ear covers , the cheeks and the chin, the feathers sometimes have black feather tips, which gives them an individually differently dotted appearance on these parts of the body. The neck, the coat and the sides of the neck are very finely dashed in white due to the whitish pen shafts that are partially visible. The eye is surrounded by a narrow ring of white feathers with very fine black pits. The outer flags of the wing covers have white feather tips. In contrast, the six outer wings of the hand on the outer flags are washed over blue, which is very noticeable in certain incidence of light.
The chin and throat are dirty white with black feather bases and greenish feather tips. As a result, these parts of the body appear very spotted. The chest is pale yellowish-green, the tone brightens towards the belly and the under tail-coverts. The lower part of the throat is dotted with white to white spots, the white center of the feathers is increasingly wider and longer, so that the lower throat and chest appear scaly. The beak is whitish with an individually different greenish tone, the iris is dark red.
Young birds are similar to adult birds, but have duller plumage. The beak is grayer, the iris reddish brown.
voice
The characteristic call of the green arboreal bird is a cat-like meow. These sounds are typical for all species of the genus Ailuroedus and have led to the English name Catbirds (German cat birds). Males call these cat-like sounds a little louder and longer than the females. The contact sounds, on the other hand, are a high tick . An imitation of bird calls, as it is typical for many arborebirds, does not occur with the green arboreal birds.
Some authors have noted that there are regional differences in the calls of the green arboreal bird. For example, the populations of green arboreal birds in the Royal National Park, south of Sydney, are considered less popular than the populations further north.
distribution
The green arboreal bird lives exclusively on the east coast of Australia. The distribution area extends from the Dawes Range in the north to the east of Canberra . The altitude distribution ranges from the lowlands to at altitudes over 1000 meters.
The green arboreal bird inhabits subtropical rainforests in this distribution area. It is also found at forest edges and in adjacent eucalyptus forests . It is particularly fond of watercourses and usually nests near them. Gardens and orchards are also visited by him, provided they are not too far from the rainforests.
food
Commonly, green arborebirds forage in pairs or small groups in the upper and middle areas of tree tops. During the winter months in particular, the green arborebird is occasionally associated with silky arborebirds and yellow-naped bowerbirds while foraging for food . On the other hand, aggressive actions occur between individual green arboreal birds when they meet in fruit-bearing trees. In fruit-bearing trees, green-arborebirds are also more assertive than fig sirole ( Sphecotheres viridis ) and long-tailed fruit pigeons . They are, however, displaced by the crested fruit pigeon and also by the yellow-naped bowerbirds.
Food composition
The green arboreal bird is an omnivore, but it feeds mainly on fruits, especially figs, flowers and other vegetable foods. It also eats invertebrates and, very rarely, young birds and small reptiles. There are several long-term studies on the feeding habits of the green arborvitae that have been carried out in different areas of its range. In the mord east of New Set Wales, green arborebirds cover 77 percent of their food needs with fruits. 7 percent of their food is blossoms, three percent are and leaves, two percent are plant stems, 1 percent are seeds and 10 percent are animal foods. In the Jimna Range in Queensland, on the other hand, fruits accounted for 68 percent, 4 percent for flowers, others 16 percent came from leaves and plant stems and another 12 percent from animal protein.
Vegetable food
As John Gould noted in the middle of the 19th century, green arborebirds show a particular predilection for the fruits of various wild fig species. Sometimes the green arboreal birds cover half of their food requirements with it. They even hoard figs on occasion. Typical after-school care places are forks of branches or small hollows in larger branches. They typically stay in a fruit-bearing tree for no more than two to three minutes. Fruits are picked directly from the branches and also eaten there.
Green arborebirds like to eat flowers and show a preference for the flowers of the species-rich orchid genus Dendrobium . In order to get to the flowers, the green arborebirds hang upside down on the orchid stems or even grab them in flight.
Animal food
They also eat grasshoppers , singing cicadas , beetles and their larvae , millipedes and tree frogs . You have also already been seen pulling a nestling of a fox tail ( Rhipidura rufifrons ) out of the nest. The proportion of insects in the green arborebird's diet increases when they raise their own offspring. Basically, the breeding season of the green arborebird falls in the time when the insect population increases seasonally. The insects are usually pecked by leaves, epiphytes, twigs, and branches. However, they occasionally catch them in the air or come on the ground to look for invertebrates. Most of the time they look for both fruit and animal food in the treetops at a height of about nine meters above the ground.
Drinking and bathing
Green arborebirds rarely come to watering places. They usually drink from the small pools of water in tree crevices and also use them for bathing. Alternatively, they take baths in the wet foliage by climbing a leafy, wet tree branch and raising and shaking their plumage.
Reproduction
District
Unlike other arborebirds, the male green arborebird does not build arbors. They are monogamous birds that enter into a partnership of several years and together defend a feeding and breeding ground. On the basis of ringed birds, it was possible to prove that a pair occupied a territory for several years. The territories of the individual green arboretum birds can overlap. The average size of the foraging area is 1.2 hectares, the breeding area is slightly smaller and is 0.6 hectares. During the time in which a clutch is incubated or young birds are raised, the parent birds rarely stay more than 56 meters from the nest. The average radius of movement of parent birds around an active nest is only 38 meters on average. During this time, only the breeding area is defended. Territory boundaries within a smaller distribution area can shift if one of the partner birds dies and a new pair forms.
Couple bond and courtship
The chases that pairs of green arboreal birds deliver were long thought to be part of courtship. However, it is now certain that these were territorial disputes and that the birds observed were not missed each other.
One of the pair bonding rituals is that the male offers the female food all year round, while the adult female shows begging behavior towards her partner bird. Mostly they are figs that the male hands over to the female. In the time before the eggs are laid, the male also offers the female insects and their larvae.
The mating of green arboreal birds was not observed in the wild until 2004. Observations are only available from captivity. The male initiated mating by sitting on a perch with food in its beak, then stretching its head and neck straight up and looking at the female. Then mating took place. Only after mating did the male hand over the food to the female.
Breeding and rearing of the young birds
The breeding season falls from mid-September to February or March, the main breeding season is from October to December. Nest building is typical in the first weeks of October, and the young birds fledge in January.
The nest is a large shell nest that is built in forks, on tree ferns or in a tangle of creepers. It is located an average of 7.1 meters above the ground. The repeated use of a rivet location has been proven, with the nest being partly built on one or more nests from previous years. Since up to now only females have been observed with nesting material or when building the nest, it is assumed that the nest is built by the female alone. Between 314 and 403 flights to obtain nesting material were counted for two nests observed for a longer period of time. The clutches are between one and three eggs in size. The majority of the clutches contain two eggs. The full freshness weight of a single egg is about 11 percent of the body weight of a female. The eggs are laid with an interval of one day. Only the female that is fed by the male breeds. The breeding season is between 23 and 24 days.
The nestling time is about 21 days. The parent birds spend about 41 percent of the day in the immediate vicinity of the nest, while the female is mostly busy huddling the young birds. It also provides about half of the food the young birds eat. The males do not roar the young, but are just as busy as the females with bringing in food. About three quarters of the nestlings are fed with fruit, the fourth quarter are animal food. Invertebrates dominate this animal diet, but it has repeatedly been observed that the parent birds also feed the nestlings of other small songbirds to their offspring. Wild figs also play a major role in the nestlings and young birds. By the time they fledge, figs are the only reliable source of food. After the fledgling, the young birds are provided with food by their parents for around 80 days.
Breeding success and predators
On average, each breeding pair of green arboreal birds grows to 1.1 young birds. Green arborebirds lay a replacement clutch when the first brood is lost. However, they generally do not raise two broods per year. The white-browed hawk has been shown to be a predator that robs nestlings of the green arboreal bird. Other predators include feral domestic cats, giant pouch martens , diamond pythons and spotted monitors .
Green arborebirds are very long-lived. Out of 100 adult birds, 97 will live to see the next year. A full-grown green arboreal bird that was ringed in October 1984 was caught again 67 times in the following years. The last recapture took place in July 1997. After reaching sexual maturity, the bird had lived on for at least 12 years and eight months.
Green arborebirds and humans
The green arboreal bird was hunted for a long time because its meat was considered delicate. It was mostly shot during hunts aimed at pigeons. Since it visits gardens and plantations more often to eat the fruit grown there, it is still occasionally shot today.
Most Australian bird parks and zoological gardens also display green arborebirds and a small number of private individuals also keep green arboreal birds. Breeding is not considered difficult.
literature
- Clifford B. Frith, Dawn. W. Frith: The Bowerbirds - Ptilonorhynchidae . Oxford University Press, Oxford 2004, ISBN 0-19-854844-3 .
- Mike Hansell: Bird nests and construction behavior , illustrated by Raith Overhill, Cambridge University Press, ISBN 0521017645 .
- Peter Rowland: Bowerbirds . Csiro Publishing, Collingwood 2008, ISBN 978-0-643-09420-8 .
Web links
- Ailuroedus crassirostris in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2004. Retrieved on January 2 of 2009.
- Videos, photos and sound recordings for Ailuroedus crassirostris in the Internet Bird Collection
Single receipts
- ↑ a b c Handbook of the Birds of the World zum Grünlaubenvogell , accessed on April 21, 2017
- ↑ a b c d e Frith: The Bowerbirds - Ptilonorhynchidae . P. 253.
- ↑ a b c d e Frith: The Bowerbirds - Ptilonorhynchidae . P. 256.
- ↑ a b Frith: The Bowerbirds - Ptilonorhynchidae . P. 250.
- ↑ a b c Frith: The Bowerbirds - Ptilonorhynchidae . P. 249.
- ↑ a b c Frith: The Bowerbirds - Ptilonorhynchidae . P. 252.
- ↑ a b c Frith: The Bowerbirds - Ptilonorhynchidae . P. 251.
- ↑ a b Frith: The Bowerbirds - Ptilonorhynchidae . P. 254.
- ↑ a b c Frith: The Bowerbirds - Ptilonorhynchidae . P. 255.