Rhinoceros bird
| Rhinoceros bird | ||||||||||
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Rhinoceros bird, male |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Buceros rhinoceros | ||||||||||
| Linnaeus , 1758 |
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The rhinoceros bird ( Buceros rhinoceros ) is a species of bird from Southeast Asia and one of the largest species in the hornbill family . The species forms a super species with the double hornbill ( Buceros bicornis ). There are two subspecies in the large distribution area of the rhinoceros bird.
Like all hornbills, the rhinoceros bird is a cave breeder. The female spends up to three months walled in a tree hollow. During this time, the male first supplies them and later also the young birds with food.
The population situation of the rhinoceros bird is indicated by the IUCN as potentially endangered ( near threatened ).
description
The rhinoceros bird reaches a size of 80 to 90 cm and a weight of 2 to 3 kilograms. In the nominate form , the average weight is 2.6 kilograms. Of the total length of this hornbill species, the male has an average of 38 centimeters and the females 35 centimeters of the tail. The beak reaches a length between 27 and 34 centimeters in the males, in the females it remains a little smaller and has a length of 22.5 to 27 centimeters. The gender dimorphism is only weak.
Appearance of the nominate form
In the male, the entire body plumage is black except for the white lower abdomen, the white thighs and the white under tail-coverts. The tail is white with a wide black transverse band in the middle.
A special feature is the large, curved beak. The basic color is pale yellow to ivory white. It gets its striking orange to orange-yellow color from the secretion of the rump gland, with which the rhinoceros bird cares for its plumage. Like many of the hornbill species, the rhinoceros bird forms a pronounced horn-like attachment made of loose bone framework. This is also colored yellowish to reddish by the rump secretion. The development of the horn attachment varies from person to person. How often the birds rub their beak and horn on branches or the like also plays a role.
Males have black rimmed red or orange eyes, females stay smaller and have red rimmed white eyes. The females also lack black markings on the beak.
Appearance of the subspecies
The division into subspecies is mainly derived from the horn shape. Because of the individual differences in the development of the horn, Kemp points out that a separation into subspecies may therefore not be justified.
The subspecies Buceros rhinoceros borneonsis (Schlegel and Müller, 1840) resembles the nominate form in terms of body plumage. However, the horn is usually a little shorter and wider and the end of the horn usually points a little more upwards. In contrast to the nominate form, the subspecies Buceros rhinoceros sylvestris (Vieillot, 1816) has a somewhat broader central band on the tail feathers. The horn usually does not point upwards at its end.
Appearance of juveniles and subadults
Young birds that have just fledged resemble adult birds in their plumage. In their case, however, the beak horn is barely developed. The orbital ring is blue-gray in them, the beak is yellow with an orange beak base. The eyes are initially light blue-gray.
Subadult birds have brown eyes by two months of age. The horn begins to develop from the age of three to four months. However, the beak and the beak horn are not fully developed even at the age of three to four years. In the case of the beak horn, growth was found in birds that had already reached an age of 8.5 years.
Possible confusion
In the distribution area of the rhinoceros hornbird there are two other large hornbill species. The hornbill belonging to the same genus has a yellow beak and a yellow beak horn . The white component in the plumage of this species is also greater. White parts of the plumage can be found on the neck, on the apex and the wings have white feather tips, which can also be seen when the wings are folded. The shield beak, which belongs to a different genus within the hornbills, has a massive horn that is reddish in color and ends abruptly in the middle of the beak. The crown and neck of this hornbill are red.
distribution and habitat
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The nominate form of the rhinoceros bird ( B. r. Rhinoceros ) is native to the Malay Peninsula and the island of Sumatra . Until 1950 the distribution area extended to Singapore. The subspecies B. r lives on Borneo . borneoensis , on Java B. r. silvestris .
The habitat is in the tropical rainforest at heights of up to 1400 m, whereby the rhinoceros bird needs primary forest , i.e. forest largely untouched by humans, due to its nesting habits . He also uses forests with selective logging and also looks for fruit-bearing trees that are near the forest edge. In general, however, he avoids open terrain and avoids flying longer distances over open terrain.
The rhinoceros bird is quite common where there are still suitable habitats for it. On the Malay Peninsula there is a pair in primary forests on 0.5 to 2.5 square kilometers. It is primarily increasing deforestation that is causing the population to decline.
General way of life
Most adult rhinoceros hornbills live in pairs and defend a territory. The flocks of up to 25 individuals observed over and over again are subadults and non-breeding sexually mature birds. Depending on the food supply, these nomadic people spread over large areas and occasionally split up into sub-groups looking for food a few hundred meters apart.
Mated rhinoceros are faithful to their location and defend a territory, but they tolerate non-breeding flocks when they cross their territory. On the other hand, they show a territorial defensive behavior towards neighboring breeding pairs. The behavior shown then primarily includes a reaction to their calls. When mated birds fly through their territory, the male always leads. If the couple is followed by a third bird, it is always the young bird.
Sunbathing is part of the comfort behavior of hornbills. They spread their wings wide and raise their tail feathers. Leaves wet with rain are used to bathe.
nutrition
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Like many hornbill species, the rhinoceros bird is omnivorous. Most of the food requirement is covered by fruits, with wild fig species rich in sugar making up 40 to 60 percent of the diet. However, rhinoceros birds are also able to break open lipid-rich capsule and stone fruits with their beak. This plays a role in their diet, especially when the supply of fruits is low. In addition to at least 13 species of different figs, the range of foods also includes nutmegs and the fruits of the oil palm, which was introduced in Asia .
About fifty percent of the time the hornbill spends foraging for food actively hunting for small vertebrates and large arthropods. It shares this behavior with many other hornbill species. Similar to these, however, it covers far less than fifty percent of its nutritional requirements with animal protein. The animals eaten include tree frogs, bird eggs, spiders and large insects such as beetles and crickets. Drongos react aggressively to rhinoceros hornbills, which is an indication that at least their eggs and young birds belong to the food spectrum of this hornbill.
The rhinoceros bird is able to meet its fluid requirements exclusively through its vegetable diet. He has never been seen drinking water.
Reproduction
Rhinoceros birds are monogamous birds. There are several indications that they occasionally raise their offspring with the help of helpers. At the end of the 19th century it was observed in a breeding cave that several young males continued to feed the female sitting in the breeding cave after the male mated with her had been shot down in the breeding cave. In rhinoceros kept in captivity, juveniles not yet sexually mature have often participated in bringing food to a pair's breeding cave. Cooperative breeding behavior has been observed in several hornbill species.
Courtship behavior
The reproductive season begins with the male increasingly courting the female with food. Such courtship behavior usually begins a month to a month and a half before the female visits the brood cavity. From this time onwards, suitable breeding caves are repeatedly sought out and inspected by the female. The males' courtship feeding intensifies before breeding begins. The two mate about 16 days before the female enters the breeding cave. Copulations sometimes occur every 30 minutes. In between there is courtship feeding by the male, intense chases and mock fights with the beaks.
Nesting duration, breeding season and clutch size
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A nesting period of 105 to 126 days has been observed in hornbills kept in human care. 37 to 46 days are spent on incubating the eggs and 78 to 80 days on the nestling period of the young birds. As with many other hornbill species, the female leaves the breeding cave before the young birds can fledge. On average it stays in the brood cavity for around three months.
The breeding season of the rhinoceros birds is not found to be a specific season. In the Malay Peninsula, egg laying has been observed in March, June and November. Rhinoceros birds brood in Java in March and April. The clutch consists of one or two eggs. However, only one young bird is raised in the wild. In the case of birds kept in human care, however, two young birds have fledged. In captive birds there was also lagging behind if the young bird died during its nestling period.
Rhinoceros do not breed every year, even if they return to their nesting burrows at least once a year. In a breeding pair observed more intensively on Borneo, the pair suspended further breeding attempts for two years.
Breeding cave and rearing of the young bird
The rhinoceros bird uses natural tree hollows at heights of 9 to 15 meters above the ground as a breeding cave. Rhinoceros have also been observed inspecting crevices in the rock. So far, however, no attempts at breeding in crevices have been reported.
Rhinoceros birds choose those breeding caves that have an elongated slot as access that is just large enough to allow the female access. Access to the brood cavity is sealed from the inside by the female alone. She mainly uses her own excrement as well as wood components from the nest cavity, which she also chews in part. Participation of the male in sealing the breeding cavity has so far only been observed in birds kept in human care. The eggs are laid after the brood cavity has been sealed. The female moults during the time in the breeding cave. In most cases, however, it does not appear to moult the large plumage at the same time. Unlike a number of other hornbill species, this would allow the female to retain her ability to fly. When the female breaks the seal of the breeding cave after about three months, leaves the breeding cave and leaves the young birds alone, the young birds independently seal the cave from within. Both the female and later the young birds only leave a narrow slit open. The male first feeds the female through this gap and later also the young birds.
The female keeps the brood cavity clean and dry by squirting her excrement through the gap. She also throws the excrement of the young birds through the gap later, as well as leftover food and similar waste. If the young birds are big enough, they excrement through the gap similar to the female.
During most of the nesting period, the male first supplies the female and later also the young bird with food. The female takes part in the feeding of the young bird as soon as it has left the breeding cave. The food is usually carried in the throat and then choked out. Figs make up a large part of the food that is brought in.
In the wild, rhinoceros that have fledged are still being fed by their parents six months after they fledged. In the case of a young bird, it was observed that months after it was already independent, it stayed in the territory of the parent birds. He only left this when a troop of subadult rhinoceros birds crossed the territory of the parent birds.
Existence and endangerment
The rhinoceros bird needs the most untouched primary forest as a habitat. As the rainforests in Southeast Asia are increasingly disappearing, especially in the accessible lowlands, the range of the rhinoceros bird is constantly decreasing. In mountainous areas, however, there is still sufficient primary forest, so that the IUCN classifies the rhinoceros bird as potentially endangered.
Rhinoceros bird and human
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The rhinoceros bird plays a role in many indigenous peoples in its range. With the Dayak Borneos, the long tail feathers are collected and used for headdresses and in traditional clothing. Skulls and horns were or are preserved, the skulls often being worked on by carving. A conspicuous aggressive behavior of this kind - namely jumping up and down on a branch as a threatening gesture - is taken up in dances of the Dayak. For the first half of the 20th century it was also described that rhinoceros birds were occasionally kept as pets.
The rhinoceros bird is the heraldic bird of the Malay state of Sarawak because it plays a role in the ethnic religions of some of Sarawak's ethnic groups. With the Iban he plays a very central role. It is therefore often reproduced in carvings.
literature
- Mark Cocker, David Tipling: Birds and People . Jonathan Cape, London 2013, ISBN 978-0-2240-8174-0 .
- Frank Gill and Minturn Wright: BIRDS OF THE WORLD Recommended English Names. Princeton University Press, 2006, ISBN 0-7136-7904-2
- Josep del Hoyo , Andrew Elliott, Jordi Sargatal: Handbook of the Birds of the World. Volume 6: Mousebirds To Hornbills. ISBN 84-87334-30-X .
- W. Grummt , H. Strehlow (Ed.): Zoo animal keeping birds. Verlag Harri Deutsch, Frankfurt am Main 2009, ISBN 978-3-8171-1636-2 .
- Alan Kemp: The Hornbills - Bucerotiformes . Oxford University Press, Oxford 1995, ISBN 0-19-857729-X .
- Theo Pagel , Bernd Marcordes: Exotic soft-eaters . Eugen Ulmer Verlag, Stuttgart 2011, ISBN 978-3-8001-5192-9 .
Web links
- Buceros rhinoceros in the endangered Red List species the IUCN 2012. Posted by: BirdLife International, 2012. Retrieved on November 4 2016th
Single receipts
- ↑ a b Buceros rhinoceros in the Red List of Threatened Species of the IUCN 2016.10. Posted by: BirdLife International, 2016. Retrieved December 23, 2016.
- ↑ a b Kemp: The Hornbills - Bucerotiformes . P. 186.
- ↑ a b c d Kemp: The Hornbills - Bucerotiformes . P. 185.
- ↑ a b Kemp: The Hornbills - Bucerotiformes . P. 184.
- ↑ a b c d e f g Kemp: The Hornbills - Bucerotiformes . P. 187.
- ↑ a b c d Kemp: The Hornbills - Bucerotiformes . P. 188.
- ↑ a b c Kemp: The Hornbills - Bucerotiformes . P. 189.