The white-necked rockfowl (Picathartes gymnocephalus) is a medium-sized bird in the family Picathartidae, with a long neck and tail. Also known as the white-necked picathartes, this passerine is mainly found in rocky forested areas at higher altitudes in West Africa from Guinea to Ghana. Its distribution is patchy, with populations often being isolated from each other. The rockfowl typically chooses to live near streams and inselbergs. It has no recognized subspecies, though some believe that it forms a superspecies with the grey-necked rockfowl. The white-necked rockfowl has greyish-black upperparts and white underparts. Its unusually long, dark brown tail is used for balance, and its thighs are muscular. The head is nearly featherless, with the exposed skin being bright yellow except for two large, circular black patches located just behind the eyes. Though the bird is usually silent, some calls are known.
These rockfowl feed primarily on insects, though parents feed small frogs to their young. One feeding strategy involves following Dorylus army ant swarms, feeding on insects flushed by the ants. Rockfowl move through the forest primarily through a series of hops and bounds or short flights in low vegetation. This species rarely flies for long distances. The white-necked rockfowl is monogamous and pairs nest either alone or in the vicinity of other pairs, sometimes in colonies with as many as eight nests. These nests are constructed out of mud formed into a deep cup and are built on rock surfaces, typically in caves. Two eggs are laid twice a year. Though the birds breed in colonies, infanticide is fairly common in this species, with rockfowl attempting to kill the young of other pairs. Nestlings mature in about a month. This bird is long-lived.
This species is classified as Vulnerable as its dwindling and fragmented populations are threatened by habitat destruction. Conservation efforts are underway in parts of its range in the form of habitat protection, education efforts, and new laws. Some of the indigenous peoples of Sierra Leone considered the species to be a protector of the home of their ancestral spirits. This rockfowl is considered one of Africa's most desirable birds by birders and is a symbol of ecotourism across its range.
Taxonomy
This species was first described by Coenraad Jacob Temminck in 1825 from a specimen collected on the Guinean coast. He published his description in the 2nd volume of Nouveau recueil de planches coloriées d'oiseaux and described it as Corvus gymnocephalus, placing it in the crow genus Corvus. The species name is derived from the Ancient Greek words gymnos "naked", and kephalē "head". However, only three years later the bird was removed from the genus Corvus by René Primevère Lesson and placed in its own genus, Picathartes, as it did not share characteristics common to members of Corvus such as a feathered head. This generic name comes from a combination of the Latin genera pica for "magpie" and cathartes for "vulture".
Since its initial description, the picathartes have been placed in more than five different families, including those of crows (Corvidae), starlings (Sturnidae), Old World flycatchers (Muscicapidae), babblers (Timaliidae) and Old World warblers (Sylviidae). Today the white-necked rockfowl and its close relative the grey-necked rockfowl are believed to comprise a unique family, Picathartidae. It has also been suggested though not generally accepted that the two rockfowl represent the remnants of an ancient bird order. Recent DNA analysis has shown that Picathartidae and its closest relatives, southern Africa's rockjumpers and southeast Asia's rail-babbler, form a clade. The analysis suggests that the rockfowl split from the common ancestor of their clade 44 million years ago. It is believed that the ancestor of this clade originated in Australia and spread to Africa. Though the white-necked rockfowl has no subspecies, it is believed to form a superspecies with the grey-necked rockfowl, with plumage and facial pattern being the primary differences between the two species.
Common names used for this species include white-necked rockfowl, white-necked picathartes, yellow-headed picathartes, bare-headed rockfowl, and the less frequently used white-necked bald crow. Rockfowl is a reference to the species' habit of building mud nests on rock surfaces and caves. Picathartes refers to the species' scientific name. Bald crow is a reference to its featherless head and somewhat crow-like appearance, especially its beak.
Description
This rockfowl measures around in length, with its notably long tail contributing about . Adult rockfowl show little sexual dimorphism in plumage and the sexes cannot be told apart by appearance. On the adult, the head, excluding the chin and throat, is completely bare of feathers except for a thin layer of fuzz on the forehead. The head's skin is bright yellow except for two large, circular patches of black skin located just behind the eye and containing the ear; only a thin, wide patch of yellow skin on the crown prevents 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 been described as a continuous, low-pitched, guttural chatter similar to "ow, ow, ow". Adults and juveniles have also been known to produce a long-drawn "owooh" call note. Additionally, fledglings can give a loud, quavering second-long whistle as a contact call.
Distribution and habitat
This species is found only in West Africa from Guinea to Ghana. It is locally common in southeastern Guinea, and is widespread in Sierra Leone except for the north and northwest, and in Liberia except for the north and northeast. In Côte d'Ivoire, the species is currently [when?] restricted to areas near the Guinean and Liberian border. The bird also lives in Ghana, where it is both local and uncommon in the south central parts of the nation. The white-necked rockfowl's total range covers approximately . However, the species occurs in low population densities in patches across this large range. The species does not migrate, though it does disperse widely after the breeding season.
This rockfowl lives on steep slopes in both primary and mature secondary forests. These forests are typically covered in rocks and are found in hilly lowland areas up to . The white-necked rockfowl often lives near flowing streams and rivers so that it has access to wet mud for nest construction. Colonies are typically found within of a stream. The species also seems to show a preference for living near inselbergs. Rockfowl are occasionally seen in partly cleared forests and near cities, but this appears to be abnormal. Recent surveys have shown that abandoned rockfowl nests are more likely to be in or near secondary forest.
Ecology and behavior
This picathartes typically keeps low in the vegetation or on the ground near its nesting grounds. It moves quickly through its forested habitat primarily through a series of hops and bounds, followed by a pause before resuming its movements. It uses its tail for balance while traversing the forest. The rockfowl also flies at a low altitude for short distances between vines and trees, and it rarely flies for long distances. This species can disappear from sight into a mass of creepers or rocks. It is capable of high jumps, sometimes jumping off the cave floor to its nest while only partly using its wings.
It was once thought that the rockfowl rarely ventures far from its breeding grounds; however, new data suggests that the species has a much broader range than previously thought. Rockfowl have been known to continue roosting on their nests for a period following the breeding season. These birds are normally solitary or in pairs, though sometimes they live in groups of three to five birds. Typically, they silently evade any unusual movements in their forest. However, if these birds know that they have been sighted, they can become quite inquisitive and occasionally approach observers. One of the rockfowl's displays entails several of the birds in a colony forming a loose circle. Individual rockfowl run at each other, forcing the approached bird to retreat slightly before chasing either the bird that charged it or another in the circle. At intervals during this display a rockfowl leans forward on a branch, tucking its head between its legs and half-spreading its wings, thus revealing its crown to the other rockfowl. It is believed that this behavior shows the intent of the rockfowl to roost in a group, though recent evidence suggests that the display could be involved in breeding. To scratch its head, the bird lifts its foot over its wing. This species is long-lived.
Diet
The white-necked rockfowl forages across slopes on mossy, creeper-covered boulders and in trees covered in lianas and hanging mosses. It occasionally forages by hopping across sand by a stream or even in the stream, as evidenced by crab remains in the rockfowl's droppings. While foraging on the ground, the rockfowl picks up leaves with its bill and tosses them aside. It feeds in mixed-species groups ahead of swarms of Dorylus ants with alethes, bristlebills, and Finsch's rufous thrushes, picking off insects flushed by the ants, mostly off the ground. The rockfowl has also been observed hopping from the ground and snatching prey midair.