Wreathed hornbill

Last updated

Wreathed hornbill
Wreathed hornbill1.jpg
Male in Pakke Tiger Reserve
Female wreathed hornbill (4039988370).jpg
Female at Ouwehands Dierenpark
CITES Appendix II (CITES) [1]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Class: Aves
Order: Bucerotiformes
Family: Bucerotidae
Genus: Rhyticeros
Species:
R. undulatus
Binomial name
Rhyticeros undulatus
(Shaw, 1812)
Synonyms

Aceros undulatus

The wreathed hornbill (Rhyticeros undulatus) is an Old World tropical bird of the hornbill family Bucerotidae, also called bar-pouched wreathed hornbill due to its distinctive blue-black band on its lower throat sac. It is named after its characteristic long, curved bill that develops ridges, or wreaths, on the casque of the upper mandible in adults. Males are black with a rufous crown, a white upper breast and face, and a yellow featherless throat. Females are uniformly black with a blue throat and are slightly smaller than males.

Contents

The wreathed hornbill ranges across the foothills and evergreen forests of Northeast India and Bhutan to Bangladesh, Southeast Asia and the Greater Sunda Islands. It is a frugivore and feeds mainly on large fruits, which it swallows whole leaving the seeds intact. This feeding behaviour plays an important ecological role for the long-distance seed dispersal in forest ecosystems.

The wreathed hornbill is threatened by hunting, habitat fragmentation and deforestation. It has been listed as Vulnerable on the IUCN Red List since 2018, as the global population is estimated to decrease due to these threats.

Taxonomy

English ornithologist George Shaw first described the species in 1812 as Buceros undulatus, based on a zoological specimen collected in Java. [2] It was placed in the genus Rhytidoceros by Daniel Giraud Elliot in 1882; [3] in Rhyticeros by Allan Octavian Hume in 1878; [4] and in Aceros by James L. Peters in 1931. [5]

The wreathed hornbill is a monotypic taxon and is widely recognized as a member of Rhyticeros, the genus of hornbills with low wreathed casques. [6] Analysis of the mitochondrial genomes of eight hornbill species revealed that the wreathed hornbill is closely related with Aceros and the Visayan hornbill (Penelopides panini). [7]

Description

Pair of adult wreathed hornbills in Pakke Tiger Reserve Wreathed Hornbill adult pair.jpg
Pair of adult wreathed hornbills in Pakke Tiger Reserve

The wreathed hornbill is black with black legs and feet, but has a pale yellow bill, bare reddish skin around the eyes, a black band around the gular skin and a white tail. The female's gular skin is blue, whereas the male's is bright yellow; his neck is white and his nape dark reddish passing into black. [8] Sexual dimorphism in the colouration of plumage and inflatable gular skin is less pronounced in young wreathed hornbills, but becomes more apparent as both sexes mature. [9]

It is a medium-sized bird with a body length of 75 to 90 cm (30 to 35 in); adult males weigh from 1.68 to 3.65 kg (3.7 to 8.0 lb), and females weigh from 1.36 to 2.69 kg (3.0 to 5.9 lb). [6]

Bill morphology

All members of the hornbill family have large, heavy bills with characteristic casques that distinguish them from other avian taxa. Hornbill casques contain foamy air-filled cavities surrounded by multiple layers of keratin tiles that act as an external shell. [10] The extra weight of the casque is supported by the fusion of the first two vertebrae. [11]

The bill has distinctive serrated casques near the base of the upper mandible, which are particularly unique because of its ridges. As the birds mature, forward growth causes the foremost ridge to break off. [9] It is hypothesized that specialized casque characteristics evolved due to multiple selection pressures, including its use for vocalization enhancement, physical pounding, mating displays, and as visual cues for age and social status. [12] [13]

Distribution and habitat

A wreathed hornbill in flight Wreathed Hornbill in Wild.jpg
A wreathed hornbill in flight

The wreathed hornbill inhabits tropical evergreen forests in the region from southern Bhutan, Northeast India, Bangladesh and through mainland Southeast Asia to Indonesia, where it is restricted to Sumatra, Java, Borneo and a few smaller islands. It has been recorded up to an elevation of 2,560 m (8,400 ft). [1]

In Bhutan, two individuals were sighted in Sarpang district in spring 1986. [14]

In Northeast India, it inhabits unlogged primary forests and selectively logged forests in the foothills of the Eastern Himalayas from Nameri National Park in Assam to Namdapha National Park in Arunachal Pradesh. [15] [16] [17] During the breeding season, it lives in lowland areas, but migrates to higher elevations in the non-breeding season. [18]

In Myanmar, 62 wreathed hornbills were sighted in the Mali River valley at elevations of 800–2,500 m (2,600–8,200 ft) in winter 1999. [19] A flock of about 50 individuals was sighted in Hponkanrazi Wildlife Sanctuary in September 2004. [20]

Behaviour and ecology

Wreathed hornbill at its nest Birds in its peaceful nest.jpg
Wreathed hornbill at its nest

The wreathed hornbill is a social bird and most active in the early mornings when foraging for fruits; 21 individuals studied in Pakke Tiger Reserve during the non-breeding season rested at midday and resumed activity in the early afternoons. [21]

It lives in larger flocks than other hornbill species and remains in groups during both breeding and non-breeding seasons. [22] Flock size observed in Namdapha National Park ranged from a mean of 4.7 to 6.6 individuals with a density of 1.3 birds/km2 (3.4 birds/sq mi) in March and April to 68 birds/km2 (180 birds/sq mi) in December. [17] In Arunachal Pradesh, the wreathed hornbill density is much lower in habitats where local people hunt, ranging from 2.9 to 9.02 birds/km2 (7.5 to 23.4 birds/sq mi). [23]

It travels long distances to forage for fruit, sometimes flying between islands, but it does not migrate. [6] A male wreathed hornbill was fitted with a GPS tracking unit in Pakke Tiger Reserve during the breeding season; it moved a mean minimum daily distance of 24.8 km (15.4 mi) and dispersed seeds for up to 10.8 km (6.7 mi) from its nesting site. [21]

Home ranges of the wreathed hornbill and other hornbill species overlap in several range countries. [9] [24]

Vocalizations

The main call of the wreathed hornbill is a loud double yelp that has been described to sound like “coo-cuk” [6] or “wuff-wurff”. [9] This call is short and typically repeated in a sequence of three or more from a perching position or during flight. [6] [9] The second part of the call is higher pitched and louder than the first and can be heard from farther distances. [9] When calling, the wreathed hornbill displays its brightly coloured throat sac by sharply thrusting its head backwards and upwards. This movement is thought to be a form of communication between individuals. [9] It makes various other low-pitched, bisyllabic barking sounds. [6]

Diet and feeding

The wreathed hornbill mainly feeds on large fruit with figs making up the majority of its diet. [22] It consumes more drupaceous fruits than other hornbill species. [25] [24] It also occasionally eats small animals like insects, crabs, snails and reptiles, particularly during the breeding season. [6] It forages in the forest canopy across its range, sometimes descending to eat small prey or to retrieve fallen fruit. [6] Tropical fruit abundance can greatly vary by location and season, therefore the wreathed hornbill flies long distances to track areas with high fruit availability. [18] As it moves across its range, it disperses the consumed seeds. The seed dispersal behaviour of the wreathed hornbill plays a critical role in maintaining tropical forest diversity. [26]

The feeding technique used by the wreathed hornbill is called ballistic food transport. [12] It holds the large food item at the tip of its bill and throws its head back quickly, swallowing it whole. This behaviour is likely to reduce resource competition by exploiting fruit that is too large for smaller frugivores. [12] Another advantage to ballistic food transport is that the fruit seeds are protected from damage when they are swallowed whole. The entire seed passes through the gastrointestinal tract and is excreted intact, increasing its chances of germination and forming a new plant. [12]

Reproduction

Wreathed hornbill emerges from its nest Wreathed Hornbill about the emerge from the nest cavity 02.jpg
Wreathed hornbill emerges from its nest

The wreathed hornbill is a monogamous breeder that demonstrates biparental care. It nests in the cavities of large trees located in coastal forests, illegally logged areas, or among foothills up to an elevation of 2,560 m (8,400 ft). [12] It searches for existing oval-shaped tree cavities for nesting because it cannot excavate its own. [27] The nest height ranges from 18 to 28 m (59 to 92 ft) above ground. [28] Females use droppings or mud to cover the nest hole to protect the clutch and fledglings from predators but leave a gap large enough for males to deliver food. [28] They unload the mud when they need to leave the nest. [28]

The average clutch size of the wreathed hornbill is 1–3 eggs, which the female incubates and guards alone for 40 days. [6] She raises only one of the chicks and remains with it in the nest until it fledges at the end of the nesting cycle, which lasts 111–137 days. Both parents remain with the juvenile for multiple months after it has left the nest. [6]

Threats

Wreathed hornbill heads in Dibang Valley Hunting Wreathed Hornbill Rhyticeros undulatus 1.jpg
Wreathed hornbill heads in Dibang Valley

Major threats to wreathed hornbill populations include hunting, use of pesticides, illegal logging and habitat fragmentation. [28] In Arunachal Pradesh, the local Mishmi and Adi people shoot 50–70 wreathed hornbills during the migratory season; they eat their meat, use their gizzards as medicine to cure stomach problems, their feathers to decorate their homes and their casques to adorn their headgear. [22] Local people also hunt wreathed hornbills for sport and use their fat for medical purposes. [1]

The wreathed hornbill has been listed as a vulnerable species on the IUCN Red List since 2018, as these threats will likely lead to a decline of the global population in the near future. [1]

Conservation

The wreathed hornbill is internationally protected under CITES Appendix II [1] and is a Class II national protected species in China. [7]

In Pakke Tiger Reserve, a community-based Hornbill Nest Adoption Program was initiated in collaboration with the Arunachal Pradesh Forest Department in 2011; local Nyishi people from nine villages worked as nest protectors and one youth as field coordinator; more than 90 urban citizens supported the project financially. In the breeding seasons of 2012 and 2013, the nest protectors located eight wreathed hornbill nests, of which two had fledgings. [29]

Related Research Articles

<span class="mw-page-title-main">Hornbill</span> Family of birds

Hornbills (Bucerotidae) are a family of bird found in tropical and subtropical Africa, Asia and Melanesia. They are characterized by a long, down-curved bill which is frequently brightly coloured and sometimes has a casque on the upper mandible. Both the common English and the scientific name of the family refer to the shape of the bill, "buceros" being "cow horn" in Greek. Hornbills have a two-lobed kidney. They are the only birds in which the first and second neck vertebrae are fused together; this probably provides a more stable platform for carrying the bill. The family is omnivorous, feeding on fruit and small animals. They are monogamous breeders nesting in natural cavities in trees and sometimes cliffs. A number of mainly insular species of hornbill with small ranges are threatened with extinction, namely in Southeast Asia.

<span class="mw-page-title-main">Yellow-casqued hornbill</span> Species of bird

The yellow-casqued hornbill, also known as the yellow-casqued wattled hornbill, is found in the rainforest of coastal regions of West Africa, for example in Côte d'Ivoire. It is threatened by habitat loss.

<span class="mw-page-title-main">African grey hornbill</span> Species of bird

The African grey hornbill is a member of the hornbill family of mainly tropical near-passerine birds found in the Old World. It is a widespread resident breeder in much of sub-Saharan Africa and the southwest of the Arabian Peninsula. The African grey hornbill has escaped or been deliberately released into Florida, USA, but there is no evidence that the population is breeding and may only persist due to continuing releases or escapes.

<span class="mw-page-title-main">Malabar grey hornbill</span> Species of bird

The Malabar gray hornbill is a hornbill endemic to the Western Ghats and associated hills of southern India. They have a large beak but lack the casque that is prominent in some other hornbill species. They are found mainly in dense forest and around rubber, arecanut or coffee plantations. They move around in pairs or small groups, feeding on figs and other forest fruits. Their loud cackling and laughing call makes them familiar to people living in the region.

<span class="mw-page-title-main">Leaf muntjac</span> Species of deer

The leaf muntjac, leaf deer or Putao muntjac is a small species of muntjac. It was documented in 1997 by biologist Alan Rabinowitz during his field study in the isolated Nogmung Township in Myanmar. Rabinowitz discovered the species by examining the small carcass of a deer that he initially believed was the juvenile of another species; however, it proved to be the carcass of an adult female. He managed to obtain specimens, from which DNA analysis revealed a new cervid species. Local hunters knew of the species and called it the leaf deer because its body could be completely wrapped by a single large leaf. It is found in Myanmar and India.

<span class="mw-page-title-main">Great hornbill</span> Bird species

The great hornbill, also known as the concave-casqued hornbill, great Indian hornbill or great pied hornbill, is one of the larger members of the hornbill family. It occurs in the Indian subcontinent and Southeast Asia. It is predominantly frugivorous, but also preys on small mammals, reptiles and birds. It has been listed as Vulnerable on the IUCN Red List since 2018. It is known to have lived for nearly 50 years in captivity. Due to its large size and colour, it is important in many tribal cultures and rituals. The Government of Kerala declared it as the official Kerala state bird.

<span class="mw-page-title-main">Rufous-necked hornbill</span> Species of bird

The rufous-necked hornbill is a species of hornbill in Bhutan, northeastern India, especially in Arunachal Pradesh, Indian Subcontinent and Southeast Asia. It is locally extinct in Nepal due to hunting and significant loss of habitat. There are less than 10,000 adults left in the wild. With a length of about 117 cm (46 in), it is among the largest Bucerotine hornbills. The underparts, neck and head are rich rufous in the male, but black in the female.

<span class="mw-page-title-main">Austen's brown hornbill</span> Species of bird

Austen's brown hornbill is a species of hornbill found in forests from northeastern India and south to Vietnam and northern Thailand. It is sometimes included as a subspecies of Tickell's brown hornbill.

<span class="mw-page-title-main">Namdapha National Park</span> National park in Arunachal Pradesh, India

Namdapha National Park is a 1,985 km2 (766 sq mi) large protected area in Arunachal Pradesh of Northeast India. The park was established in 1983. With more than 1,000 floral and about 1,400 faunal species, it is a biodiversity hotspot in the Eastern Himalayas. The national park harbours the northernmost lowland evergreen rainforests in the world at 27°N latitude. It also harbours extensive dipterocarp forests, comprising the northwestern parts of the Mizoram-Manipur-Kachin rain forests ecoregion.

<span class="mw-page-title-main">Blyth's hornbill</span> Species of bird

Blyth's hornbill, also known as the Papuan hornbill, is a large hornbill inhabiting the forest canopy in Wallacea and Melanesia. Its local name in Tok Pisin is kokomo.

<span class="mw-page-title-main">Bucerotiformes</span> Order of birds

Bucerotiformes is an order of birds that contains the hornbills, ground hornbills, hoopoes and wood hoopoes. These birds were previously classified as members of Coraciiformes. The clade is distributed in Africa, Asia, Europe and Melanesia.

<span class="mw-page-title-main">Knobbed hornbill</span> Species of bird

The knobbed hornbill, also known as Sulawesi wrinkled hornbill, is a colourful hornbill native to Indonesia. The species is sometimes placed in the genus Aceros. The knobbed hornbill is the faunal symbol of South Sulawesi province.

<span class="mw-page-title-main">Narcondam hornbill</span> Species of bird

The Narcondam hornbill is a species of hornbill in the family Bucerotidae. It is endemic to the Indian island of Narcondam in the Andamans. Males and females have a distinct plumage. The Narcondam hornbill has the smallest home range out of all the species of Asian hornbills.

<span class="mw-page-title-main">Plain-pouched hornbill</span> Species of bird

The plain-pouched hornbill is a species of hornbill in the family Bucerotidae. It is found in forests of the Dawna Range and the Tenasserim Hills of southern Myanmar, adjacent parts of western Thailand and northern Peninsular Malaysia.

<span class="mw-page-title-main">Oriental pied hornbill</span> Species of bird

The oriental pied hornbill is an Indo-Malayan pied hornbill, a large canopy-dwelling bird belonging to the family Bucerotidae. Two other common names for this species are Sunda pied hornbill (convexus) and Malaysian pied hornbill.

<span class="mw-page-title-main">Brown-cheeked hornbill</span> Species of bird

The brown-cheeked hornbill is a species of hornbill in the family Bucerotidae. It is found in Ivory Coast, Ghana, Guinea, Liberia, Sierra Leone, and Togo. Its natural habitats are tropical and subtropical moist broadleaf forests, plantations, and secondary growth forests. It is threatened by habitat destruction, as timber is harvested and the forests become increasingly fragmented.

<i>Aglaia spectabilis</i> Species of tree found near the Pacific and Indian coasts

Aglaia spectabilis is a species of tree in the family Meliaceae, found from the Santa Cruz Islands in the southwest Pacific to Queensland (Australia), Southeast Asia, Yunnan (Zhōngguó/China) and the Indian subcontinent. It grows from a 1m shrub to an emergent 40m tall tree, depending on the habitat. Its wood is commercially exploited as timber, but otherwise is of poor quality with limited use. The fruit are eaten, and used in folk medicine. The seeds are large in comparison to other plants, and a major source of dispersal of the species are hornbills eating the fruit, flying away from the tree and regurgitating the seeds.

<i>Rhyticeros</i> Genus of birds

Rhyticeros is a genus of medium to large hornbills found in forests from Southeast Asia to the Solomons. They are sometimes included in the genus Aceros. On the other hand, most species generally placed in Aceros are sometimes moved to Rhyticeros, leaving Aceros as a monotypic genus only containing the rufous-necked hornbill.

Pakke Tiger Reserve, is a Project Tiger reserve in the East Kameng district of Arunachal Pradesh in Northeast India. The 862 km2 (333 sq mi) reserve is protected by the Department of Environment and Forest of Arunachal Pradesh. It was known as Pakhui Tiger Reserve, but renamed in April 2001 by the Governor of Arunachal Pradesh. It has won India Biodiversity Award 2016 in the category of 'Conservation of threatened species' for its Hornbill Nest Adoption Programme.

<i>Horsfieldia kingii</i> Species of tree

Horsfieldia kingii is a dioecious tree of the family Myristicaceae. It grows up to 20 m tall and has large seeds that are dispersed by frugivores such as hornbills and imperial pigeons. The fruiting period is from February to May. The fruit is an arillate capsule and is bi-coloured.

References

  1. 1 2 3 4 5 6 BirdLife International (2018). "Rhyticeros undulatus". IUCN Red List of Threatened Species . 2018: e.T22682528A132400385. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22682528A132400385.en . Retrieved 26 January 2022.
  2. ↑ Shaw, G. (1811). "Undulated Hornbill". In Shaw, G.; Stephens, J.F. (eds.). General zoology, or Systematic natural history. Vol. Volume 8, Part 1: Aves. London: G. Kearsley. pp. 26–27.
  3. ↑ Elliot, D.G. (1882). "Rhytidoceros undulatus. Wreathed Hornbill". A monograph of the Bucerotidæ, or family of the hornbills. London: Taylor and Francis. pp. 1–2.
  4. ↑ Hume, A.O. & Davidson, W. (1878). "A revised list of the birds of Tenasserim". Stray Feathers. 6: 1–496.
  5. ↑ Peters, J.L. (1931). "Genus Aceros". Check-list of Birds of the World. Vol. V. Cambridge: Harvard University Press. pp. 263–266.
  6. 1 2 3 4 5 6 7 8 9 10 Kemp, A.C. & Boesman, P.F.D. (2020). "Wreathed Hornbill (Rhyticeros undulatus)". In del Hoyo, J.; Elliott, A.; Sargatal, J. & Christie, D.A. (eds.). Handbook of the Birds of the World. Vol. Volume 6: Mousebirds to Hornbills. Barcelona: Lynx Edicions. ISBN   978-8487334306.
  7. 1 2 Chen, Y.; Yan, H.; Sun, J.; Li, C.; Xiao, H. & Chen, S. (2019). "Characterization and phylogenetic analysis of the complete mitochondrial genome sequence of Rhyticeros undulatus (Bucerotiformes: Bucerotidae)". Conservation Genetics Resources. 11 (1): 27–30. doi:10.1007/s12686-017-0957-0. S2CID   31607039.
  8. ↑ Blanford, W.T. (1889). "Rhyticeros undulatus. The Malayan Wreathed Hornbill". The Fauna of British India, including Ceylon and Burma. Vol. Birds – Volume III. London: Taylor and Francis. pp. 147–146.
  9. 1 2 3 4 5 6 7 Frith, C.B. & Douglas, V.E. (1978). "Notes on ten Asian hornbill species (Aves: Bucerotidae) with particular reference to growth and behaviour" (PDF). Natural History Bulletin of the Siam Society. 27: 35–82.
  10. ↑ Seki, Y.; Bodde, S.G. & Meyers, M.A. (2010). "Toucan and hornbill beaks: A comparative study". Acta Biomaterialia. 6 (2): 331–343. doi:10.1016/j.actbio.2009.08.026. PMID   19699818.
  11. ↑ Kinnaird, M.F. & O'Brien, T.G. (2007). "The rise of Hornbills: Evolution, taxonomy, and morphology". The Ecology and Conservation of Asian Hornbills: Farmers of the Forest. Chicago: University of Chicago Press. pp. 19–50. ISBN   9780226437125.
  12. 1 2 3 4 5 Baussart, S. & Bels, V. (2011). "Tropical hornbills (Aceros cassidix, Aceros undulatus, and Buceros hydrocorax) use ballistic transport to feed with their large beaks". Journal of Experimental Zoology Part A: Ecological Genetics and Physiology. 315A (2): 72–83. doi:10.1002/jez.590. PMID   20140955.
  13. ↑ Gamble, K.C. (2007). "Internal anatomy of the hornbill casque described by radiography, contrast radiography, and computed tomography". Journal of Avian Medicine and Surgery. 21 (1): 38–49. doi:10.1647/1082-6742(2007)21[38:IAOTHC]2.0.CO;2. JSTOR   27823461. PMID   18069170. S2CID   19495666.
  14. ↑ Clements, F. (1992). "Recent records of birds from Bhutan" (PDF). Forktail. 7: 57–73.
  15. ↑ Saikia, P.K. & Saikia, M.K. (2011). "Present distribution, status, and ecology of White-winged Wood Duck and Hornbills in Nameri National Park, considering the tropical forest disturbances of Assam". Zoo's Print. 26 (11): 1–11.
  16. ↑ Datta, A. (1998). "Hornbill abundance in unlogged forest, selectively logged forest and a forest plantation in Arunachal Pradesh, India". Oryx. 32 (4): 285–294. doi: 10.1046/j.1365-3008.1998.d01-58.x .
  17. 1 2 Naniwadekar, R. & Datta, A. (2013). "Spatial and temporal variation in hornbill densities in Namdapha Tiger Reserve, Arunachal Pradesh, north-east India". Tropical Conservation Science. 6 (6): 734–748. doi: 10.1177/194008291300600603 . S2CID   54872934.
  18. 1 2 Naniwadekar, R.; Mishra, C. & Datta, A. (2015). "Fruit resource tracking by hornbill species at multiple scales in a tropical forest in India". Journal of Tropical Ecology. 31 (6): 477–490. doi:10.1017/S0266467415000449. S2CID   83830161.
  19. ↑ King, B.; Buck, H.; Ferguson, R.; Fisher, T.; Goblet, C.; Nickel, H. & Suter, W. (2001). "Birds recorded during two expeditions to North Myanmar (Burma)". Forktail. 17: 29–40.
  20. ↑ Renner, S.C.; Rappole, J.H .; Milensky, C.; Myint Aung; Nay Myo Shwe & Thein Aung (2015). "Avifauna of the southeastern Himalayan mountains and neighboring Myanmar hill country" (PDF). Bonn Zoological Bulletin. Supplementum (62): 1–75.
  21. 1 2 Naniwadekar, R.; Rathore, A.; Shukla, U.; Chaplod, S. & Datta, A. (2019). "How far do Asian forest hornbills disperse seeds?" (PDF). Acta Oecologica. 101: 103482. Bibcode:2019AcO...10103482N. doi:10.1016/j.actao.2019.103482. S2CID   208589706.
  22. 1 2 3 Krishna, C.M.; Sarma, K. & Kumar, A. (2012). "Rapid assessment of Wreathed Hornbill Aceros undulates (Aves: Bucerotidae) populations and conservation issues in fragmented lowland tropical forests of Arunachal Pradesh, India". Journal of Threatened Taxa. 4 (14): 3342–3348. doi: 10.11609/JoTT.o2969.3342-8 .
  23. ↑ Dasgupta, S. & Hilaluddin (2012). "Differential effects of hunting on populations of hornbills and imperial pigeons in the rainforests of the Eastern Indian Himalaya". Indian Forester. 138 (10): 902–909.
  24. 1 2 Poonswad, P. & Tsuji, A. (1994). "Ranges of males of the Great Hornbill Buceros bicornis, Brown Hornbill Ptilolaemus tickelii and Wreathed Hornbill Rhyticeros undulatus in Khao Yai National Park, Thailand". Ibis. 136 (1): 79–86. doi:10.1111/j.1474-919X.1994.tb08133.x.
  25. ↑ Leighton M. & Leighton, D.R. (1983). "Vertebrate responses to fruiting seasonality within a Bornean rain forest". In Sutton, S L.; Whitmore, T.C. & Chadwick, A.C. (eds.). Tropical Rain Forest: Ecology and Management. Oxford: Blackwell Scientific Publications. pp. 181–196.
  26. ↑ Naniwadekar, R.; Mishra, C.; Isvaran, K. & Datta, A. (2021). "Gardeners of the forest: hornbills govern the spatial distribution of large seeds". Journal of Avian Biology. 52 (11): first view. doi: 10.1111/jav.02748 .
  27. ↑ Utoyo, L.; Marthy, W.; Noske, R.A. & Surahmat, F. (2017). "Nesting cycle and nest tree characteristics of the Helmeted Hornbill Rhinoplax vigil, compared to the Wreathed Hornbill Rhyticeros undulatus, in Sumatran lowland rainforest". Kukila. 20: 12–22.
  28. 1 2 3 4 Rahayuningsih, M.; Kartijono, N.E. & Retnoningsih, A. (2017). "Short Communication: The nest characteristics of Wreathed Hornbill (Rhyticeros undulatus) in Mount Ungaran, Central Java, Indonesia". Biodiversitas. 18 (3): 1130–1134. doi: 10.13057/biodiv/d180334 .
  29. ↑ Rane, A. & Datta, A. (2015). "Protecting a hornbill haven: a community-based conservation initiative in Arunachal Pradesh, northeast India". Malayan Nature Journal. 67 (2): 203–218.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.