The rufous-necked hornbill (Aceros nipalensis) 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 , it is among the largest Bucerotine hornbills. The underparts, neck and head are rich rufous in the male, but black in the female. Taxonomy The scientific name Buceros nipalensis was coined by Brian Houghton Hodgson in 1829 who described several rufous-necked hornbills caught by hunters in sal forest in Nepal. It was placed in the genus Aceros by John Edward Gray in 1844. Description The head, neck, and lower body of the male are coloured rufous, with deeper colouration on the flanks and abdomen. The middle primaries and the lower half of the tail are tipped white. The rest of the hornbill's plumage is a glossy dark-green and black. The lower tail-covert feathers are coloured chestnut mixed with black. The female is black, except for the end-portion of her tail and the tips of the middle primaries, which are white. Juvenile hornbills resemble adults of the same sex, but lack the ridges at the base of the upper beak. The beak lacks a true caique but is thickened at its base. It has a number of dark ridges on the upper beak which are absent in the young and increase in number with age up to about seven. The commissure of the beaks is broken in both sexes. Distribution and habitat The rufous-necked hornbill has the northernmost distribution ranging from Northeast India, central Bhutan to western Thailand and northwestern Vietnam. It ranges over an area of , of which is forested. Within this area, it lives in 90 protected areas comprising of protected forest but only including 7% of optimal hornbill habitat. Mahananda Wildlife Sanctuary in West Bengal represents its westernmost limit; it has also been recorded in Buxa Tiger Reserve, Manas National Park, Eaglenest Wildlife Sanctuary, Sessa Orchid Sanctuary, Kamlang Wildlife Sanctuary, Namdapha National Park and Pakke Tiger Reserve. It predominantly inhabits ridged and hilly forests, primarily temperate broadleaf and mixed forests at elevations of , It has also been recorded in dry woodland. Behaviour and ecology The nesting period is from March to June, the trees preferred are tall and have broad girths. These hornbill