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Aceros and Achaetops. A-Z of Bird genera.Part -3

Updated on September 29, 2015




In this series we are reviewing the A-Z of bird genera,which will look at species of birds from all over the globe. Here we review the genus Aceros which is a genus of birds commonly refrred to as Hornbills, of the family Bucerotidae. The genus sometimes includes all the species placed in the genus Rhyticeros.

Some authorities only include the Rufous -necked Hornbill,and place all the others in the genus Rhyncheros. To complicate matters further the White crowned Hornbill that was once placed in the genus Aceros has now been placed in the genus Berenicornis.

However, by most authorities there are five recognized species in the genus Aceros.

Rufous -necked Hornbill. Aceros nipalensis.

Taken in India
Taken in India | Source

A look at the species.

The Rufous-necked Hornbill, Aceros nipalensis, is native to north eastern India and south east Asia. Sadly this species is currently classed as Vulnerable. It is estimated that only 10,000 adults remain. This is due to habitat loss and over hunting.

It is a large bird with an impressive down-curved bill. The males have a rufous head and neck and under parts with black and white wings. The females are dark brown to black all over. There is a ring of bare blue skin around the red eyes and the bill is yellow with black and white,almost bar-code like stripes.

The females have an extraordinary life style,she spends up to four months of the year ,within an hollow tree at her nest. With the help of her mate she seals herself into the hole which is generally located between 6-33 metres above the ground. To achieve this they use semi-digested leaves,oil globules and regurgitated mud. The only aperture is a slit through which the male will feed her and her resulting chicks.

The female will lay 1-2 eggs in April. The incubation period is timed to continue throughout the dry season,so that when the chicks hatch it coincides with the rainy season. It may be as long as 125 days before she finally breaks the seal and leaves the tree hole, the chicks follow her shortly afterwards.

The birds feed on fruit such as nutmegs,pears and figs,but will also take other fruits that are ripe at the time. They are also known to take beetles,lizards,earthworms frogs and even small birds. The species is also found in China,Thailand,Laos,and Vietnam. They are now thought to be extinct in Nepal.

They are slow growing but long-lived birds that produce few offspring each season and thus they are vulnerable to over-hunting. The birds are hunted in China and Vietnam in particular,despite laws that have been introduced to protect them.

Aceros cassidix

Taken on North Sulawesi.
Taken on North Sulawesi. | Source

Aceros cassidix pair.

Taken at Walsrode Bird Park Germany.
Taken at Walsrode Bird Park Germany. | Source

Aceros cassidix.

Aceros cassidix, is referred to by the common names of Knobbed Hornbill and the Sulawesi Wrinkled Hornbill. The general plumage of this large Hornbill is black with the exception of the white tail feathers. They have a pale blue skin around the eye and a bare dark blue throat,and yellow bill.

The male has a rufous/buff face and neck,a yellow casque { A prominent bony structure on top of the bill that meets the head.} . it is endemic to Indonesia a bird of tropical evergreen forests of Sulawesi, Buton, Lembeth, Togian and Mina islands.

They breed in high densities in the Tanykoko-DuaSudara Nature reserve,North Sulawesi, Indonesia. these birds are known to be a useful disperser of many tropical tree seeds. Although they are widespread and relatively common throughout their native range,they are listed as being vulnerable by the IUCN. { International Union for the conservation of nature.}

Aceros corrugatus

Taken at Zoo, Negara Malaysia.
Taken at Zoo, Negara Malaysia. | Source

Aceros corrugatus.

Aceros corrugatus, is the Wrinkled Hornbill or the Suda Wrinkled Hornbill, some times placed in the genus Buceros. It is a medium to large bird around 70 cm { two and half feet} has a very large bill fused to the skull. They are birds of the Thai-Malaysia Peninsular.

It gains its common name from its yellowish red casque on top of its bill which in this species is rigid and wrinkled. The male has a deep yellow bill with a reddish base,and a wrinkled red/orange casque. The males are surrounded by a rim of light blue skin,while the sides of the head,upper breast and tail are white,the neck is bright yellow.

The body plumage is black including the wings and tail with a metallic green sheen. The female however, is smaller than the male and completely black with the exception of the yellow bill and casque and a distinguishing blue neck. Her casque is also smaller than that of the male.

These birds feed on a diet of fruit,especially drupes and figs. Although they have been known to feed in small groups they generally feed in pairs,they are not thought to be territorial During the breeding season,generally during the rainy season ,December to January,and after mating has occurred the female finds a deep tree hole to nest in.

She will then seal herself in ,in the manner already described above, and remain in the nest with her eggs and succeeding chicks until they fledge. The male will feed her and the chicks through a slit in the seal. The seal is broken when the chicks are ready to emerge.

This is another species classed by the I.U.C.N., as Near Threatened,this is mainly due to habitat loss through illegal and widespread logging.It is thought that they are on the verge of extinction in Thailand.

Aceros leucocephalus


Writhed Hornbill. Aceros leaucocephalus.

The Writhed Hornbill is endemic to the humid forests on the Philippine Islands of Mindano, Dunagat, and Camiguin Sur. It is known by several common names such as the Mindanao Wrinkled Hornbill, White-eared Hornbill, and the White -headed Hornbill. And by some authorities placed in the genus Buceros.

The male has a red bill and a red wrinkled casque. It has a blue black grooves on the base of the lower mandible,and bare orange red skin around the eyes and throat. The crown and nape are dark brown. The neck,face and upper breast are white. They have a black body and wings. The long white tail is tipped with black.

The female has a pale orange facial skin as is the casque,which is not wrinkled, or much less so than that of the male,and the blue black grooves on the lower mandible are smaller. The head, neck and throat,like the rest of her plumage is black.

This species is listed by the I.U.N.C. as Near threatened. Apart from habitat loss these birds are hunted. The skull and tail feathers are used to make traditional costumes for ceremonies and the casque is also utilized for ornamental carvings,and the bill is used to make jewelry.

Aceros waldeni. Painting of a male carrying fruit.

Painting by Professor Eberland,Curio, Rhur University Bochum Germany.
Painting by Professor Eberland,Curio, Rhur University Bochum Germany. | Source

Walden's Hornbill. Aceros waldeni.

Walden's Hornbill, Aceros waldeni,is currently listed by the I.U.C.N ,a s Critically Endangered,in its native range of Negros and Panay, in the Philippines,where it is a bird of rainforests. it is also known by the common names of Visayan Wrinkled Hornbill, Rufous headed Hornbill, and Writhed -Hornbill. This species like the previous species has wrinkled casque of a reddish colour on top of the red bill. It is a medium sized bird with predominantly black plumage,glossed with a green sheen, and a large white band on the centre of the tail which is conspicuous when in flight.

The malle has a striking reddish head,neck and upper breast. The facial skin is a bright saffron yellow. In the female the throat and ocular skin are blue, which differentiates them from the Writhed Hornbill {above}, whose throat and ocular skin are a deep orange in both sexes.

Their breeding habits are similar to all Hornbills previously mentioned.

Aceros undulatus-Female


Aceros undulatus -Male

Rotterdam Zoo, Netherlands.
Rotterdam Zoo, Netherlands. | Source

Wreathed Hornbill. Aceros undulatus.

The Wreathed Hornbill, Aceros Undulatus, syn, Rhyticeros undulatus, is also referred to as the Bar-pouched wrinkled Hornbill. They are birds native to the forests of north eastern India and Bhutan,and through the mainland of south eastern Asia. they are similar to the species Aceros subruficollis {below}, however, this species can be distinguished by the dark bar on the lower throat. {see Image right }

They are not a species of concern. The casque in this species is just a flat wrinkled wreath at the bottom of the base of the bill,their are cross ridges on the beak.. The plumage in general is black with a short white tail. The male has the crown and nape a dark red brown colour. The inflatable throat pouch is yellow.The female has a blue throat pouch. The bill and casque are light coloured with brownish markings.

They are, in common with other Hornbills, mainly fruit eaters,but will also take invertebrates.

Aceros subruficollis

The Plain Pouched Hornbill, Aceros subruficollis, is found in the forests of the Dawn range and the Tenasserina Hills of south Burma,as well as the adjacent parts of western Thailand and the northern peninsular of Malayer..

The species is classed as being Vulnerable by the I.U.C.N. due to habitat loss. The yellow throat pouch of this species lacks the black bar line at the base,hence its common name.

Aceros plicatus { Rhyticeros plicatus}

Upoloaded and derivative work by Snowmanradio.  The image was taken at Lincoln Park Zoo Chicago. USA.
Upoloaded and derivative work by Snowmanradio. The image was taken at Lincoln Park Zoo Chicago. USA. | Source



Aceros plicatus

Aceros plicatus,syn, Rhyticeros plicatus,is known by the common names of Blythe's Hornbill or the Papuan Hornbill. It is a bird that frequents the forest canopy in Wallacea { A group of mainly Indonesian islands } and Melanasia, a group of islands that includes Vanualku, Solomon Islands, Fiji and Papua New Guinea.

The common name of Blythe's Hornbill, commemorates Edward Bythe 1810-1873, an English Zoologist. various sub species have been described across its range. Six at least are recognized. Blythe's Hornbill, is up to thirty six inches long. The male is generally of a black colour with a white throat and tail. The head however, is orange buff, the throat is white. The iris is reddish brown,and the eye is surrounded by a naked pale blue skin patch. The female is smaller with a white throat and tail the rest of her plumage is black.

The pale horn-coloured casque on the large horn-coloured bill may have as many as eight folds on the adult birds. Their breeding habits are the same as for all Hornbills.

Aceros comatus. Male right. Female left.


Aceros comatus.

Aceros comatus, The White -Crowned Hornbill, is sometimes placed in the genus Berenicornis.It is also referred to by the common names of Long -Crested Hornbill, or White -Crested Hornbill. It must not be mistaken for the African White Crowned Hornbill of the genus Torpicanus {albocristatus}, which is also sometimes placed in the genus Berenicornus albocristatus.

It is a large species of up to 40 inches long and weighs 33 pounds. The female is smaller than the male The plumages in general is black and white. The white parts being the head, breast, neck and tail. The head is adorned with a crown of feathers erected into a crest. Between the eye and the bill and on the throat there is a patch of dark blue skin. The bill is dark with a yellowish base. It has a black casque on top of the bill,often hidden by the feathers. The female has a black neck and under parts.

This species, is found,in the main, in the rainforest at low altitudes on the Malay Peninsular,Sumatra and Borneo,where they feed on fruit, lizards and invertebrates. The breeding habits are the same as other Hornbills, the female sealing herself inside a tree hole and being fed by the male until the chicks are ready to leave.

This species is classed as being Near threatened by the IUCN. This due to habitat destruction in their native range.

The genus Achaetops

The genus Achaetops has only one current member. Achaetops pygnopygius,commonly known as the 'Rock Runner '., or the Damora rock-jumper. It is a species of African warbler formerly placed in the genus Sylviidae. It is encountered in Angola and Nambia.

Illustration of the Rock Runner



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    • D.A.L. profile image

      Dave 2 years ago from Lancashire north west England

      Hi Deb,

      Doing this series is educating me,by way of research . I hope that one day you get to Papua New Guinea, and find the birds you love. Best wishes to you.

    • aviannovice profile image

      Deb Hirt 2 years ago from Stillwater, OK

      Utterly fascinating. These hornbills, none of which I know, are quite large and remarkable. In view of their use to plant trees and other important foodstuffs, it would be such a shame for them to become extinct. Regarding Papua, New Guinea, this is where my secondary specialty of the birds of paradise are located. I do so hope to get there to find as many as I can, and perhaps see at least one hornbill.

    • D.A.L. profile image

      Dave 2 years ago from Lancashire north west England

      Hello Devika ,

      Thank you for tweeting and your comments you are very kind and encouraging. Best wishes to you.

    • DDE profile image

      Devika Primić 2 years ago from Dubrovnik, Croatia

      I tweeted! Amazing creations!