the two black patches from connecting. The black patch has a raised edge and appears to be a distinct part of the face. The eyelid and eyering are a thin line of black surrounding the bird's large, dark brown eyes. The beak is robust, disproportionately large, and black. This beak can be considered crow-like, is noticeably decurved in the upper mandible, and is about long. The bird's chin and throat are covered in a thin layer of white feathers, and the neck is long and slender. The nape is also covered in white feathers, while the hindneck is nearly bare, revealing the orange-yellow skin. The upper mantle is a solid black, merging into a greyish-black lower mantle. The rockfowl's thighs are very muscular and aid its partially terrestrial lifestyle. The back, rump, and undertail are a bluish grey, while the tail is a dark brown and tented in shape. The moderately-sized wings are also a dark brown. The underparts are a creamy white and appear their creamiest in the upper breast. In dim light the white-necked rockfowl can appear to be solely black above and white below. The legs are blue and relatively long. Overall the plumage appears to be smooth with long feathers. The adult weighs . The nestling is born naked with dark-brown skin above and translucent pink skin below, blind, and with an orange-red gape. After a few days, the gape changes to a bright yellow-orange. After hatching, the head's skin is all yellow without the black patches of the adult; these are gained about a week before leaving the nest. An immature rockfowl after its fourth week is very similar to the adult, but its underparts are creamier and silkier than those of the adult, its neck possesses fewer feathers, and the yellow on the head is paler. Most noticeably, its tail is significantly shorter than that of the adult. Although numerous calls have been recorded, the white-necked rockfowl is normally a silent bird. Its call has been compared to the clucks of a chicken, with clucks of "chuk-chuk-chuk" or "choop-choop-choop" being made at a constant rate of eight notes every five seconds. This call typically lasts for at least a minute. It has been suggested that this call may be a proper song, but more research is required to determine if this is accurate. The rockfowl's alarm call, one of its more frequent sounds, has