Silver cheek hornbill
| Silver cheek hornbill | ||||||||||||
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Great Hornbill in Sylvan Heights Waterfowl Park, Scotland Neck, North Carolina |
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| Bycanistes brevis | ||||||||||||
| Friedmann , 1929 |
The silver cheek hornbill ( Bycanistes brevis ) is a monotypical bird species from the hornbill family . Its distribution area is East Africa. Like all hornbills, the silver cheek hornbill is also a cave breeder. The female spends up to four months walled in a tree cavity and only leaves the nest cavity together with the fledglings that have fledged. During this time, the male first supplies them and later also the young birds with food.
The IUCN states that the silver hornbill is not at risk ( least concern ).
features
The silver cheek hornbill reaches a body length of 66 to 74 centimeters. The tail feathers account for an average of 27.6 centimeters in males and 26 centimeters in females. The males have a beak between 15.3 and 19.5 centimeters. The beak of the females remains slightly smaller and is 13.8 to 15.5 centimeters in length. The male's beak is in the shape of an upside-down chopping knife and is a dirty white color, the smaller of the female is the same brownish color as the beak.
The body plumage of the male is predominantly shiny black, the facial feathers have narrow silver-gray tips. The end of the back, the rump, the upper tail and lower tail and the belly are white. The control feathers are black and have white tips except for the middle pair of tail feathers. The wings are black. The beak is brownish with a narrow dirty yellow band at the base of the beak. The featherless skin around the eye is blue, the eyes are brown, the legs and feet are black.
Fledglings have plumage that is similar to that of adult birds. However, the feathers on the base of the beak and on the sides of the face have brown hems. The beak is still small, the tip of the beak not or hardly developed. The eyes are pale cream in color.
The flight of the silver cheek hornbird is noisy. The voice is loud and sounds like a rough grunt, similar to that of the gray-cheeked hornbird.
Possible confusion
The silver-cheeked hornbill can hardly be confused with other hornbills in its range: It is the only tree-dwelling hornbill species with a black head, wings and coat, as well as a white back and rump. The male's beak is not found in any other species. It can best be distinguished from species belonging to the same genus such as the trumpeter hornbill ( B. buccinator ) and the gray-cheeked hornbill ( B. subcylindricus ) by its completely black wings. The trumpeter hornbill, whose range partially overlaps with that of the silver cheek hornbill, is also smaller and has a black beak attachment.
distribution and habitat
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The silver cheek hornbill lives in eastern Africa. The distribution area is disjoint , because the hornbill is dependent on contiguous forest areas and these are not continuously available.
The highlands in southern Ethiopia belong to its range . It is also found in Somalia , Kenya and from Tanzania to Malawi . The extreme north-east of South Africa is also part of its range. The main areas of distribution include the east of the Great Rift Valley and the Mount Kenya massif . In mountain regions it occurs at altitudes up to 2500 meters, in the lowlands it is a pure forest inhabitant. It also colonizes gallery forests along rivers. It is the most common hornbill in the mountain forests of northern Tanzania and in the coastal forests of Kenya. Outside of the breeding season, it undertakes long migrations to meet its food needs. During the dry season, it can be found outside of the forest areas that are typical for it. This is particularly the case when, after rainfall, in otherwise unsuitable habitats, it offers sufficient food.
Way of life
Silver cheek hornbills live in pairs. Occasionally, the couple is also accompanied by this year's young bird. However, young birds occasionally form separate groups. Several pairs can often be found on fruit-bearing trees. Where the food supply is very rich, up to 100 silver cheek hornbills can occasionally congregate. The silver cheek hornbill is often associated with trumpeter hornbills and then shares resting and feeding areas with them. The hornbill leaves its resting places about half an hour after sunrise and returns to them before sunset.
The silver-cheeked hornbill is mostly in the treetops, where it picks fruit directly from the branches and twigs. He occasionally comes to the ground to look for insects or to pick up fruit that monkeys have dropped. He also occasionally takes dust baths on the floor.
The crowned eagle , one of the largest eagles in Africa, is considered a predator of the silver-cheeked hornbird.
nutrition
Like most hornbills, the silver-cheeked hornbill is omnivorous. However, it covers a large part of its nutritional needs with fruits. Like many hornbill species, figs play a particularly important role in its diet. He prefers cherry-sized fruits and also eats small, hard-shelled nuts. For food spectrum include the fruits and seeds of Rauwolfia , Eugenia , strychnos , Syzygium and Acokanthera . It may play a large role in plant reproduction by dropping larger, non-digestible seeds about fifty feet from the fruiting tree. He swallows smaller seeds and excretes them with his excrement. Sticky mistletoe berries that stuck to the beak are stripped off the beak at its next resting place.
In addition to fruit, the hornbill also eats bird eggs, nestlings, skinks , chameleons , caterpillars, grasshoppers and crickets, praying mantises, termites, spiders and centipedes . He has also been observed catching red-nosed green pigeons , an African species of fruit pigeon that reaches a body length of 30 centimeters and is therefore only slightly smaller than a city pigeon . Mated silver-cheeked hornbills hunt individually, but stay close to each other and indicate their presence to the partner bird through soft contact calls. They show extremely aggressive behavior during the hunt. For example, they jump up and down on branches to scare off prey. Smaller teams also attack together dormant bats .
Reproduction
Silver cheek hornbills are monogamous birds. They do not defend a breeding area, but only the immediate vicinity of the nest cavity. Here, however, the male shows a decidedly antagonistic behavior towards males of the same species. The clutch consists of one or two eggs. In the wild, however, two young birds only grow up in exceptional cases.
Incubation period and duration
The breeding season depends on the respective geographic distribution. In Ethiopia, for example, silver-cheeked hornbills breed between February and July. In Tanzania, on the other hand, from August to September. Basically, the beginning of the breeding season in the south of the distribution area seems to be dependent on the onset of rainfall. Due to the long riveting time, the fledglings of the young birds coincide with the end of the rainy season.
The actual start of breeding is preceded by a phase in which the male repeatedly offers food to the female as a courtship act. The actual nesting period is between 107 and 138 days. Of this, around 40 days are spent on incubating the eggs and 77 to 80 days on the nestling period. The female only leaves the breeding cave when the offspring also fly out. It does moult during this time, but it does not seem to moult the large plumage simultaneously and thus retains its ability to fly.
The female and later the young birds are fed in their time in the brood cavity by the male, which produces around 24,000 fruits during this time. It also flies to the breeding cave about 1600 times. On average, there are around 360 grams of fruit a day that the male brings in the throat or beak.
Breeding cave
Silver-cheeked birds usually use natural tree hollows as breeding caves, which are between 7 and 25 meters above the ground. The use of rock caves has also been described in isolated cases. Suitable breeding caves are repeatedly used by the hornbill for breeding attempts.
For a hornbill species, the intense involvement of the male in sealing the breeding cave is comparatively unusual. With most hornbill species, it is the female alone who closes them up to a narrow gap. In the silver cheek hornbill, the male carries up to 235 globules per day to the breeding cavity, which it salivates in its throat. The saliva acts as a binding agent, not the female's feces, as is the case with most other hornbills. At the breeding cave, the male passes the saliva-filled globules, which have a diameter of 1.5 to 2.5 centimeters, to the female, who uses them to wall the breeding cave up to a narrow gap. The male's ability to produce sufficient saliva-insulated globules is a major limiting factor in the reproduction of the silver-cheeked hornbill. Sealing of the brood cavity can take months until the brood cavity has been prepared enough for the couple to proceed to the brood. The first mating occurs about ten days before the female finally moves into the brood cavity. This is not preceded by any specific actions.
Breeding course
During the breeding season, the male brings not only food but also bits of bark and small branches. They probably serve to cushion the nest cavity and keep it clean. More closely examined breeding caves showed a significantly different insect infestation than empty breeding caves immediately after leaving the female and young bird. In the previously occupied breeding cave, larvae and nymphs of cockroaches, flies, beetles and moths were found.
At the end of the breeding cycle, the female and the young bird leave the breeding cave. Mostly this is done in the early morning hours. The female and young bird break open the seal of the breeding cave together. The young bird is immediately ready to fly and does not return to the brood cave.
Silver cheek hornbills only raise two young birds in rare cases. It is also typical of this species that they do not brood every year and that they frequently interrupt their attempt at breeding. The brood is occasionally broken off even after the offspring have hatched. However, termination at an earlier stage is more typical. With more intensive observations of silver-cheeked birds, between four and six young birds fledged in eight breeding attempts.
Trivia
The British ornithologist Reginald Ernest Moreau has done extensive research on the birds. On his field observations carried out in the 1940s, essential knowledge about the reproductive behavior of this species is based to this day.
literature
- Mark Cocker, David Tipling: Birds and People. Jonathan Cape, London 2013, ISBN 978-0-2240-8174-0 .
- 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 .
- G. Mauersberger: Urania animal kingdom, birds. Urania, 1991, ISBN 3-332-00491-3 , p. 308.
- JG Williams, N. Arlott: A field guide to the birds of East Africa. Collins, London 1980, ISBN 0-00219179-2 .
- Frieder Sauer : Sauer's natural guide. African birds. Fauna.
Web links
- BirdLife International (2009) Species factsheet: Bycanistes brevis. http://www.birdlife.org Accessed August 11, 2009.
- Bycanistes brevis inthe IUCN 2012 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved December 6, 2016.
- Videos, photos and sound recordings of Silvery-cheeked Hornbill (Bycanistes brevis) in the Internet Bird Collection
Single receipts
- ↑ a b c d e Kemp: The Hornbills - Bucerotiformes . P. 260.
- ↑ Bycanistes brevis in the IUCN Red List of Threatened Species 2012.5. Listed by: BirdLife International, 2012. Retrieved December 6, 2016.
- ↑ a b c Kemp: The Hornbills - Bucerotiformes . P. 257.
- ↑ Kemp: The Hornbills - Bucerotiformes . P. 256.
- ↑ a b c d e Kemp: The Hornbills - Bucerotiformes . P. 258.
- ↑ Gerhard Rösler: The wild pigeons of the earth - free life, keeping and breeding . M. & H. Schaper Verlag, Alfeld-Hannover 1996, ISBN 3-7944-0184-0 , p. 258
- ↑ a b c d e f g Kemp: The Hornbills - Bucerotiformes . P. 259.