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. 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 1811 as Buceros undulatus, based on a zoological specimen collected in Java. It was placed in the genus Rhytidoceros by Daniel Giraud Elliot in 1882; in Rhyticeros by Allan Octavian Hume in 1878; and in Aceros by James L. Peters in 1931. The wreathed hornbill is a monotypic taxon and is widely recognized as a member of Rhyticeros, the genus of hornbills with low wreathed casques. 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). Description 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. 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. It is a medium-sized bird with a body length of ; adult males weigh from , and females weigh from . Bill morphology All members of the hornbill family have large, heavy bills with