Grey-necked Rockfowl
Encyclopedia
The Grey-necked Rockfowl (Picathartes oreas) is a medium-sized bird
in the family Picathartidae with a long neck and tail. Also known as the Grey-necked Picathartes, this passerine
is mainly found in rocky areas of close-canopied rainforest from southwest Nigeria through Cameroon, Equatorial Guinea, and southwest Gabon. It additionally lives on the island of Bioko
. Its distribution is patchy, with populations often isolated from each other. The rockfowl typically chooses to live near streams and inselbergs in its forested habitat. It has no recognized subspecies, though some believe that it forms a superspecies
with its close relative, the White-necked Rockfowl
. The Grey-necked Rockfowl has grey upperparts, a light grey breast, and lemon-colored underparts. Its unusually long tail is used for balance, and its thighs are muscular. The head is nearly featherless, with the exposed skin being powder blue on the forehead and upper mandible
and carmine on the hindcrown. The bird’s cheeks and eyes are covered in a large, circular black patch that, though narrow, connects and divides the carmine and powder blue skin at the peak of the crown. Though the bird is usually silent, some calls are known.
This rockfowl feeds primarily on insects, though some plant matter, such as fruit and flower buds, is eaten. One feeding strategy involves following Dorylus
army ant swarms, feeding on insects flushed by the ants
. Rockfowl move through the forest mainly through a series of hops and bounds, or short flights in low vegetation. It travels either alone or in small groups. This species rarely flies for long distances. The Grey-necked Rockfowl is monogamous and pairs nest either alone or in the vicinity of other pairs, sometimes in colonies of two to five nests, though one colony of forty nests has been recorded. These nests are constructed out of mud and are formed into a deep cup that is built on rock surfaces, typically in caves or on cliffs. Two eggs are laid twice a year. Though the birds breed in colonies, infanticide exists in this species, with rockfowl attempting to kill the young of other pairs. Nestlings mature in about a month.
This species is classified as Vulnerable
as its dwindling and fragmented populations are threatened by habitat destruction. A conservation plan has been drawn up for this species, and research into its current distribution is ongoing. Some of the indigenous peoples of Cameroon either respect this species or, in some cases, fear it. Today, this rockfowl is considered one of Africa’s most desirable birds by birders and is a symbol of ecotourism
across its range.
by Anton Reichenow
in 1899 from a bird collected at the base of Mount Cameroon
near Limbe, Cameroon. He published his description in Ornithologische Monatsberichte and described it as Picathartes oreas. The generic name was first used by René-Primevère Lesson
in 1828 after he split the Grey-necked Rockfowl's close relative the White-necked Rockfowl
from the crow genus Corvus
and placed it in its own genus, Picathartes, as the White-necked Rockfowl 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". The species name is derived from the Ancient Greek
word oreas, meaning "mountain". 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 Grey-necked Rockfowl and the White-necked Rockfowl are believed to comprise a unique family, Picathartidae. Additionally, it has 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 Grey-necked Rockfowl has no subspecies
, it may form a superspecies
with the White-necked Rockfowl, with plumage and facial pattern being the main differences between the two species.
This species has numerous common names, including the Grey-necked Rockfowl, Grey-necked Picathartes, Bare-headed Rockfowl, Red-headed Rockfowl, Blue-headed Picathartes, and Grey-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 in its beak.
. The adult's head is largely featherless, and the skin on the forehead and forecrown as well as the upper mandible
of the beak
behind the bird's nostril is a powder blue. The lower mandible and rest of the upper mandible are black. This beak is unusually large and crow-like at 30 millimetres (1.2 in) in length and is also decurved. There are some small, bristle-like feathers located on the crown that can be erected. Behind the crown, the species' bare skin on the hindcrown and nape is carmine
in coloration and has a few more bristle-like feathers. The area between these patches of skin, as well as the lores, cheeks, and ear region, are featherless with black skin. Its eyes are dark brown. The Grey-necked Rockfowl's mantle, back, rump, and uppertail coverts are all grey. The feathers on the rump are long, dense, and silky. Additionally, the tail is grey. The rockfowl's chin, throat, sides of the neck, and upper breast are all a pale grey. This bird is buffy lemon in color on its lower breast, belly, flanks, thighs, and undertail coverts, though the flanks can sometimes appear to be greyish. The wing is grey, though the wing's remiges are black, forming a line between the lemon underparts and grey upperparts. Its legs and feet are silver-grey and muscular. The adult rockfowl weighs 200 to 250 g (7.1 to 8.8 oz).
The nestling is born nearly featherless except for tiny primary quills and a fine down along its spine, humerus
, forearm, and femur
. Its skin is dark pink but displays variable black patches on its upperside. The gape is yellow. As the nestling develops, its plumage begins to resemble that of the adult, though it has white flecks on its wing coverts and the featherless skin on the head is black or dark brown, not powder blue, on the forecrown and dark reddish brown, not carmine, on the hindcrown. After fledging, the immature closely resembles the adult except for the bare patch on the back of the head being golden yellow instead of carmine and the tail being only a third as long as that of an adult.
The Grey-necked Rockfowl is a relatively silent species. It has been known to give a quiet, one to two second long, hissing "wheet" call several times at intervals of about four seconds. To give this call, the rockfowl opens its beak and inflates its throat. When bringing food to their nests, the adults give one or two "peep"s. After reaching the nest, the adult repeatedly makes a low "ga-a-a" sound that has been described as being between a snore and a sigh. It also makes a hissing noise that has been described as a "shisss".
The Grey-necked Rockfowl is found in West Africa from southeast Nigeria to southwest Gabon. In Nigeria, it is only found in the nation's southeastern corner near the coast and the Cameroon border. The species is widespread in southwestern Cameroon, and this country is considered to be the species' stronghold. It is found throughout Equatorial Guinea and into southwestern Gabon. Additionally, the species resides in the southwestern forests of the island of Bioko
in the Gulf of Guinea
. There is only one record of this species from the Republic of the Congo, though it is suspected that the rockfowl may have an undiscovered population in this country. The Grey-necked Rockfowl's total range covers approximately 314000 square kilometres (121,236.1 sq mi).
It is found in undisturbed rain forests with closed canopies. The Grey-necked Rockfowl prefers rugged terrain in these forests covered in large boulders, caves, and gorges. Additionally, it often found near inselbergs and a source of water, either a river or a forest pool. The understory of its forests has sparse undergrowth or open spaces but is covered in mosses, ferns, liana
s, and epiphytes. In southwestern Bioko
it is found in low forests that receive nearly 10 metres (32.8 ft) of rain a year. Bioko's habitat also has dense undergrowth and vertical gorges near a caldera
. The rockfowl's habitat is normally found between 450 and 2100 m (1,476.4 and 6,889.8 ft) above sea level, though it is lower in elevation on Bioko. This species is non-migratory, and at one site in Cameroon the birds remained within 300 metres (984.3 ft) of their nesting site throughout the year. It is capable of living near human activity, and one breeding site in Cameroon was located within 30 metres (98.4 ft) of a maize
plot. This and other recent observations suggest that the rockfowl has greater tolerance for degraded habitat than previously thought.
-tangled areas or in caves away from the nests. To scratch its head, the species lifts its foot over its head. It bathes in small pools. While its lifespan in the wild is unknown, it has lived up to 25 years in captivity.
ants, feeding on the insects flushed by the ants. It also is known to hunt in streams for crabs and fish. It crushes snails with its beak and, if its prey struggles, smashes it against the ground. While an uncommon occurrence, male rockfowl have been observed giving food to a female.
The Grey-necked Rockfowl feeds on a diverse range of invertebrates and small vertebrate
s, though plant matter does constitute a major part of its diet. It is known to eat beetles, including weevil
s, rove beetle
s, and click beetle
s from the genus Psephus, butterflies, ants from the genera Dorylus
and Pachycondyla
, grasshopper
s, cockroaches from the family Blattidae
, earwig
s, caterpillar
s, ant-lions, silverfish
, and earthworms. Small lizards, frogs, snails, and slugs are also eaten, as are crabs from the genus Potamon
, fruit
s, flower buds, moss
es, and leaves
. Fish have also been identified as a prey item in Nigeria. At at least one nesting site, it relies heavily on the arthropods feeding on the bat guano
near the cave for sustenance, while this behavior has been reported to a lesser extent at other sites. It is known to regurgitate what it has eaten in pellet form. Overall, between 52 and 60 percent of the bird's diet is believed to be composed of animals. Rove beetle larvae and ants were the most frequently eaten prey in a study in Nigeria.
and therefore does not breed with rockfowl other than its mate. It is believed to breed cooperatively in Equatorial Guinea, as four different birds were observed feeding one nest. The rockfowl's courtship displays are unknown. The timing of the egg laying in a colony is not synchronized, leading to various stages of development of nestlings within the colony. It has been suggested that this is to promote cooperative breeding. The laying dates also vary by region, typically coinciding with a few weeks before the onset of the wet season; in areas where the wet season is bimodal, two different breeding seasons occur. However, in mountainous regions such as Mount Cameroon, it breeds during the dry season to avoid the frequent mists of the wet season. Birds in Nigeria lay their eggs between August and November, birds in Gabon lay between November and April, birds in western Cameroon lay between March and November with peaks of June, July, and October, and birds in southern Cameroon have two breeding seasons, a main one from October to December and a secondary one lasting from April to May. In Equatorial Guinea, nesting occurs in mid-February.
This rockfowl builds its nest onto the sides of rocks, normally in caves, where nests are built both by the entrance and deep within, or on nearly vertical cliff faces, which can be either bare or have some vegetation, though never woody branches, near the nest. Nests need to be built under an overhang to protect it from water, and the rock surface normally slopes forward slightly. The nests are almost always found near water, which can be in the form of either streams or forest pools. These streams, particularly those located at the base of a nesting cliff, help keep predators away from the nests. Nests on rock surfaces are normally built 1.2 to 5.2 m (3.9 to 17.1 ft) above the ground. In addition to the rock face nests, there is a record of a nest being constructed on the buttress root
of a Piptadeniastrum
tree above a small stream. Two nests were even built onto a concrete bridge in Gabon's Lopé National Park
. The male and female rockfowl work equally on the nest's construction, and it can take two to three months to build one, though in some extreme cases it takes more than a year. The nest itself is a half-cup constructed of dry mud with grass fibers and dead leaves mixed in, often with the plant matter sticking out of the nest's walls. It is either built onto the rock surface or, in some cases, is built more like a retaining wall across the opening of a small rock fissure. Nests are built at least away 1 metres (3.3 ft) from each other, and in some cases up to 5 metres (16.4 ft). The nest is normally 30 to 40 cm (11.8 to 15.7 in) thick, though the nest is uneven in its construction and one nest was 140 centimetres (55.1 in) thick. It is about 290 centimetres (114.2 in) wide and 400 centimetres (157.5 in) long and weighs about 3 kilograms (6.6 lb). However, nest sizes do have a large degree of variability. After the mud dries, it becomes a very hard structure. The inside of the nest is lined with rootlets and thin strips of grass.
One to three eggs, normally two, are laid, with the second egg being laid between 24 and 48 hours after the first. The eggs are variable in coloration and can be a light yellow-brown with dark brown blotches, creamy white with dark brown or grey blotches, or pale grey with brown mottling. The eggs weigh about 15.2 gram (0.536164223997702 oz) and have an average size of 40.5 millimetres (1.6 in) by 27.5 millimetres (1.1 in). The rockfowl begins to incubate
after both eggs are laid. The time the rockfowl spends incubating varies greatly, though it is mostly for less than five minutes at a time with nearly two hours between sessions. Both the male and female rockfowl incubate. When the incubating bird's mate comes, it gives a brief call that causes the incubating bird to leave the nest. In the two days prior to hatching, the adult rockfowl prods at the eggs, sometimes with food in its beak. Incubation lasts for 21 to 24 days. When the infants hatch, they hatch about a day apart. The adult rockfowl quickly remove the eggshell fragments from the nest. The newborn weighs only 12 gram (0.423287545261344 oz) after hatching, but it quickly gains weight. The eyes open and the tail begins to grow on the fifth day. During the first couple of days, food is brought to the nestlings three to six times an hour, peaking in the evening. Begging nestlings expose their beak and gape to their parent, though they do not make a sound. The second-hatched nestling often fails to gain weight and dies, and there is evidence suggesting that the adults cannibalize the remains. For the first ten days after hatching, one adult rockfowl stays and guards the nestlings while the other collects food; despite this, nests have been destroyed by chimpanzee
s and drills
. The chicks leave the nest after 24 days. Infanticide has been recorded in this species, with rockfowl killing other rockfowl's young. In one case, a second pair of rockfowl moved onto a nest after killing the first pair's nestlings.
made this species a target on two of his trips to Cameroon, which he describes in The Bafut Beagles
and A Zoo in My Luggage
. The trade of this species is non-existent today, and, as the zoo population did not sustain itself despite sporadic breeding, the last captive rockfowl died at the Frankfurt Zoo in 2009. The Grey-necked Rockfowl has been depicted on numerous postage stamps from Cameroon and Nigeria, as well as stamps from Benin and Togo, where it does not live. It is considered one of the most difficult species of bird to see in the wild. The Grey-necked Rockfowl is a symbol for both conservation and ecotourism efforts in its range. This species is considered one of the five most desirable birds in Africa by ornithologists.
The Grey-necked Rockfowl is considered to be Vulnerable
due to habitat destruction, its isolated populations, collection of adults, predation, and a low breeding success rate. Its habitat is being destroyed to create large agricultural fields and cocoa plantations, as well as for logging and slash-and-burn agriculture. Due to the highly specialized requirements for its habitat, its population is very fragmented, and the species is believed to be naturally rare. Competition for its nesting sites is a result of these strict requirements and can lead to infanticide. Its estimated population is between 2,500 and 10,000 individuals, though it is believed that the population is at the lower end of the estimate. However, due to the inaccessibility of some parts of its range, it is also possible that this species is more common than believed. The population of some of these colonies is reaching the minimum levels needed for long-term viability. It also falls victim to spring traps set for mammals by hunters. However, a more serious threat to its numbers was the widespread collection of rockfowl for display in zoos in the 1950s and 1960s. There is a risk that it will be negatively affected by ecotourism due to disturbances in its daily routine if proper viewing procedures are not followed.
Cameroon is the only nation with a national law protecting this species. This law prohibits killing the rockfowl, though it can be captured with a proper permit. International trading of the Grey-necked Rockfowl is governed under CITES Appendix I, meaning that legal trading of this species is only authorized in extraordinary circumstances. In 2006 BirdLife International
drafted an international action plan to provide strategies for protecting this species. This plan focused on surveying the remaining habitat, raising awareness amongst the local populace, and limiting the continued destruction of its habitat.
This rockfowl is protected in some of the areas in which it lives by national parks. Additionally, there seems to be little habitat destruction in Gabon and on Bioko as the locations in these places in which the rockfowl lives is believed to be too inaccessible for future human development. Recent surveys have also discovered new populations of the Grey-necked Rockfowl.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
in the family Picathartidae with a long neck and tail. Also known as the Grey-necked Picathartes, this passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
is mainly found in rocky areas of close-canopied rainforest from southwest Nigeria through Cameroon, Equatorial Guinea, and southwest Gabon. It additionally lives on the island of Bioko
Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...
. Its distribution is patchy, with populations often isolated from each other. The rockfowl typically chooses to live near streams and inselbergs in its forested habitat. It has no recognized subspecies, though some believe that it forms a superspecies
Superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...
with its close relative, the White-necked Rockfowl
White-necked Rockfowl
The White-necked Rockfowl 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...
. The Grey-necked Rockfowl has grey upperparts, a light grey breast, and lemon-colored underparts. Its unusually long tail is used for balance, and its thighs are muscular. The head is nearly featherless, with the exposed skin being powder blue on the forehead and upper mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
and carmine on the hindcrown. The bird’s cheeks and eyes are covered in a large, circular black patch that, though narrow, connects and divides the carmine and powder blue skin at the peak of the crown. Though the bird is usually silent, some calls are known.
This rockfowl feeds primarily on insects, though some plant matter, such as fruit and flower buds, is eaten. One feeding strategy involves following Dorylus
Dorylus
The army ant genus Dorylus, also known as driver ants, safari ants, or siafu, is found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by...
army ant swarms, feeding on insects flushed by the ants
Ant-follower
Ant-followers are birds that feed by following swarms of army ants and take prey flushed by those ants. The best known ant-followers are 18 species of antbird in the family Thamnophilidae, but other families of birds may follow ants including thrushes, chats, ant-tanagers, cuckoos, and...
. Rockfowl move through the forest mainly through a series of hops and bounds, or short flights in low vegetation. It travels either alone or in small groups. This species rarely flies for long distances. The Grey-necked Rockfowl is monogamous and pairs nest either alone or in the vicinity of other pairs, sometimes in colonies of two to five nests, though one colony of forty nests has been recorded. These nests are constructed out of mud and are formed into a deep cup that is built on rock surfaces, typically in caves or on cliffs. Two eggs are laid twice a year. Though the birds breed in colonies, infanticide exists in this species, with rockfowl attempting to kill the young of other pairs. Nestlings mature in about a month.
This species is classified as Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
as its dwindling and fragmented populations are threatened by habitat destruction. A conservation plan has been drawn up for this species, and research into its current distribution is ongoing. Some of the indigenous peoples of Cameroon either respect this species or, in some cases, fear it. Today, this rockfowl is considered one of Africa’s most desirable birds by birders and is a symbol of ecotourism
Ecotourism
Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...
across its range.
Taxonomy
This species was first describedSpecies description
A species description or type description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously, or are...
by Anton Reichenow
Anton Reichenow
Anton Reichenow was a German ornithologist.Reichenow was the son-in-law of Jean Cabanis, and worked at the Humboldt Museum from 1874 to 1921. He was an expert on African birds, making a collecting expedition to West Africa in 1872 and 1873, and writing Die Vögel Afrikas...
in 1899 from a bird collected at the base of Mount Cameroon
Mount Cameroon
Mount Cameroon is an active volcano in Cameroon near the Gulf of Guinea. Mount Cameroon is also known as Cameroon Mountain or Fako or by its native name Mongo ma Ndemi ....
near Limbe, Cameroon. He published his description in Ornithologische Monatsberichte and described it as Picathartes oreas. The generic name was first used by René-Primevère Lesson
René-Primevère Lesson
René Primevère Lesson was a French surgeon, naturalist, ornithologist, and herpetologist.Lesson was born at Rochefort, and at the age of sixteen he entered the Naval Medical School there...
in 1828 after he split the Grey-necked Rockfowl's close relative the White-necked Rockfowl
White-necked Rockfowl
The White-necked Rockfowl 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...
from the crow genus Corvus
Crow
Crows form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-size jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several...
and placed it in its own genus, Picathartes, as the White-necked Rockfowl 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". The species name is derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
word oreas, meaning "mountain". Since its initial description, the picathartes have been placed in more than five different families, including those of crows (Corvidae
Corvidae
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs and nutcrackers. The common English names used are corvids or the crow family , and there are over 120 species...
), starlings (Sturnidae), Old World flycatchers (Muscicapidae), babblers (Timaliidae) and Old World warblers (Sylviidae
Sylviidae
Sylviidae is a family of passerine birds that was part of an assemblage known as the Old World warblers. The family was formerly a wastebin taxon with over 400 species of bird in over 70 genera. The family was poorly defined with many characteristics shared with other families...
). Today the Grey-necked Rockfowl and the White-necked Rockfowl are believed to comprise a unique family, Picathartidae. Additionally, it has 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
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
. 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 Grey-necked Rockfowl has no subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, it may form a superspecies
Superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...
with the White-necked Rockfowl, with plumage and facial pattern being the main differences between the two species.
This species has numerous common names, including the Grey-necked Rockfowl, Grey-necked Picathartes, Bare-headed Rockfowl, Red-headed Rockfowl, Blue-headed Picathartes, and Grey-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 in its beak.
Description
This rockfowl measures approximately 33 to 38 cm (13 to 15 in) in length, with its notably long tail contributing about 14 centimetres (5.5 in). This species does not show sexual dimorphismSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. The adult's head is largely featherless, and the skin on the forehead and forecrown as well as the upper mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
of the beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
behind the bird's nostril is a powder blue. The lower mandible and rest of the upper mandible are black. This beak is unusually large and crow-like at 30 millimetres (1.2 in) in length and is also decurved. There are some small, bristle-like feathers located on the crown that can be erected. Behind the crown, the species' bare skin on the hindcrown and nape is carmine
Carmine
Carmine , also called Crimson Lake, Cochineal, Natural Red #4, C.I. 75470, or E120, is a pigment of a bright-red color obtained from the aluminum salt of carminic acid, which is produced by some scale insects, such as the cochineal beetle and the Polish cochineal, and is used as a general term for...
in coloration and has a few more bristle-like feathers. The area between these patches of skin, as well as the lores, cheeks, and ear region, are featherless with black skin. Its eyes are dark brown. The Grey-necked Rockfowl's mantle, back, rump, and uppertail coverts are all grey. The feathers on the rump are long, dense, and silky. Additionally, the tail is grey. The rockfowl's chin, throat, sides of the neck, and upper breast are all a pale grey. This bird is buffy lemon in color on its lower breast, belly, flanks, thighs, and undertail coverts, though the flanks can sometimes appear to be greyish. The wing is grey, though the wing's remiges are black, forming a line between the lemon underparts and grey upperparts. Its legs and feet are silver-grey and muscular. The adult rockfowl weighs 200 to 250 g (7.1 to 8.8 oz).
The nestling is born nearly featherless except for tiny primary quills and a fine down along its spine, humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, forearm, and femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
. Its skin is dark pink but displays variable black patches on its upperside. The gape is yellow. As the nestling develops, its plumage begins to resemble that of the adult, though it has white flecks on its wing coverts and the featherless skin on the head is black or dark brown, not powder blue, on the forecrown and dark reddish brown, not carmine, on the hindcrown. After fledging, the immature closely resembles the adult except for the bare patch on the back of the head being golden yellow instead of carmine and the tail being only a third as long as that of an adult.
The Grey-necked Rockfowl is a relatively silent species. It has been known to give a quiet, one to two second long, hissing "wheet" call several times at intervals of about four seconds. To give this call, the rockfowl opens its beak and inflates its throat. When bringing food to their nests, the adults give one or two "peep"s. After reaching the nest, the adult repeatedly makes a low "ga-a-a" sound that has been described as being between a snore and a sigh. It also makes a hissing noise that has been described as a "shisss".
Distribution and habitat
Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...
in the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
. There is only one record of this species from the Republic of the Congo, though it is suspected that the rockfowl may have an undiscovered population in this country. The Grey-necked Rockfowl's total range covers approximately 314000 square kilometres (121,236.1 sq mi).
It is found in undisturbed rain forests with closed canopies. The Grey-necked Rockfowl prefers rugged terrain in these forests covered in large boulders, caves, and gorges. Additionally, it often found near inselbergs and a source of water, either a river or a forest pool. The understory of its forests has sparse undergrowth or open spaces but is covered in mosses, ferns, liana
Liana
A liana is any of various long-stemmed, woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy to get access to well-lit areas of the forest. Lianas are especially characteristic of tropical moist deciduous...
s, and epiphytes. In southwestern Bioko
Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...
it is found in low forests that receive nearly 10 metres (32.8 ft) of rain a year. Bioko's habitat also has dense undergrowth and vertical gorges near a caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
. The rockfowl's habitat is normally found between 450 and 2100 m (1,476.4 and 6,889.8 ft) above sea level, though it is lower in elevation on Bioko. This species is non-migratory, and at one site in Cameroon the birds remained within 300 metres (984.3 ft) of their nesting site throughout the year. It is capable of living near human activity, and one breeding site in Cameroon was located within 30 metres (98.4 ft) of a maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
plot. This and other recent observations suggest that the rockfowl has greater tolerance for degraded habitat than previously thought.
Ecology and behavior
This rockfowl usually lives either alone or in pairs, although small flocks of three to ten birds are not uncommon. It normally moves through its habitat in a series of runs and long, springing hops on the ground and in low branches. It uses its tail for balance while hopping and running. When in a flock, rockfowl hop almost in unison. In the unusual occurrences when the species does fly, it is fast and is capable of navigating through the trees and rocks well. When it is standing still, the rockfowl has its tail down and its head looking up. Typically, it silently evades 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. This is not a shy species once it knows that it has been seen, and often studies things of interest, including humans, from an open location. When this species is suspicious, it raises the small crown on its head and the ruff on its neck while uttering a muffled groan. It is most active in the early morning and late evening, and from 10:30 am to 7:00 pm remains perched with little activity either in lianaLiana
A liana is any of various long-stemmed, woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy to get access to well-lit areas of the forest. Lianas are especially characteristic of tropical moist deciduous...
-tangled areas or in caves away from the nests. To scratch its head, the species lifts its foot over its head. It bathes in small pools. While its lifespan in the wild is unknown, it has lived up to 25 years in captivity.
Diet
This species forages in the early morning or late afternoon either alone or in small groups in leaf litter and on dead tree trunks. It is also known to leap upwards to grab prey on overhanging foliage. It looks for its prey either by standing still and scanning the surrounding area or by tossing the leaf litter away with its beak. It also frequently follows columns of DorylusDorylus
The army ant genus Dorylus, also known as driver ants, safari ants, or siafu, is found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by...
ants, feeding on the insects flushed by the ants. It also is known to hunt in streams for crabs and fish. It crushes snails with its beak and, if its prey struggles, smashes it against the ground. While an uncommon occurrence, male rockfowl have been observed giving food to a female.
The Grey-necked Rockfowl feeds on a diverse range of invertebrates and small vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, though plant matter does constitute a major part of its diet. It is known to eat beetles, including weevil
Weevil
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
s, rove beetle
Rove beetle
The rove beetles are a large family of beetles, primarily distinguished by their short elytra that leave more than half of their abdomens exposed. With over 46,000 species in thousands of genera, the group is the second largest family of beetles after the Curculionidae...
s, and click beetle
Click beetle
The family Elateridae is commonly called click beetles , elaters, snapping beetles, spring beetles or "skipjacks". They are a cosmopolitan beetle family characterized by the unusual click mechanism they possess...
s from the genus Psephus, butterflies, ants from the genera Dorylus
Dorylus
The army ant genus Dorylus, also known as driver ants, safari ants, or siafu, is found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by...
and Pachycondyla
Pachycondyla
Pachycondyla is a diverse group of ponerine ants that are widespread in the world's tropics and subtropics. Most are general predators or scavengers, with some specializing in hunting termites. In some species queens are replaced by fertilised workers...
, grasshopper
Grasshopper
The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...
s, cockroaches from the family Blattidae
Blattidae
The Blattidae is a family of the order Blattaria . It contains several of the most common household cockroaches.-Selected species:*Oriental cockroach *American cockroach...
, earwig
Earwig
Earwigs make up the insect order Dermaptera, found throughout the Americas, Africa, Eurasia, Australia and New Zealand. With 1,800 species in 12 families, they are one of the smaller insect orders...
s, caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s, ant-lions, silverfish
Silverfish
Lepisma saccharina, frequently called silverfish, fishmoths, carpet sharks or paramites, are small, wingless insects in the order Thysanura...
, and earthworms. Small lizards, frogs, snails, and slugs are also eaten, as are crabs from the genus Potamon
Potamon
Potamon, in Greek mythology, is one of the sons of Aegyptus and Caliadne. He married Glaucippe, one of the Danaids, daughter of Danaus and Polyxo....
, fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s, flower buds, moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es, and leaves
Leaves
-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...
. Fish have also been identified as a prey item in Nigeria. At at least one nesting site, it relies heavily on the arthropods feeding on the bat guano
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...
near the cave for sustenance, while this behavior has been reported to a lesser extent at other sites. It is known to regurgitate what it has eaten in pellet form. Overall, between 52 and 60 percent of the bird's diet is believed to be composed of animals. Rove beetle larvae and ants were the most frequently eaten prey in a study in Nigeria.
Reproduction
The Grey-necked Rockfowl breeds either alone or in small colonies averaging two to five nests in size, though nearly fifty nests are present at one site. It is monogamousMonogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
and therefore does not breed with rockfowl other than its mate. It is believed to breed cooperatively in Equatorial Guinea, as four different birds were observed feeding one nest. The rockfowl's courtship displays are unknown. The timing of the egg laying in a colony is not synchronized, leading to various stages of development of nestlings within the colony. It has been suggested that this is to promote cooperative breeding. The laying dates also vary by region, typically coinciding with a few weeks before the onset of the wet season; in areas where the wet season is bimodal, two different breeding seasons occur. However, in mountainous regions such as Mount Cameroon, it breeds during the dry season to avoid the frequent mists of the wet season. Birds in Nigeria lay their eggs between August and November, birds in Gabon lay between November and April, birds in western Cameroon lay between March and November with peaks of June, July, and October, and birds in southern Cameroon have two breeding seasons, a main one from October to December and a secondary one lasting from April to May. In Equatorial Guinea, nesting occurs in mid-February.
This rockfowl builds its nest onto the sides of rocks, normally in caves, where nests are built both by the entrance and deep within, or on nearly vertical cliff faces, which can be either bare or have some vegetation, though never woody branches, near the nest. Nests need to be built under an overhang to protect it from water, and the rock surface normally slopes forward slightly. The nests are almost always found near water, which can be in the form of either streams or forest pools. These streams, particularly those located at the base of a nesting cliff, help keep predators away from the nests. Nests on rock surfaces are normally built 1.2 to 5.2 m (3.9 to 17.1 ft) above the ground. In addition to the rock face nests, there is a record of a nest being constructed on the buttress root
Buttress root
Buttress are large roots on all sides of a big bottomed tree or shallowly rooted tree. Typically, they are found in nutrient-poor rainforest soils and do not penetrate to deeper layers. They prevent the tree from falling over while also gathering more nutrients...
of a Piptadeniastrum
Piptadeniastrum
Piptadeniastrum is a genus of flowering plants in the legume family, Fabaceae. It belongs to the subfamily Mimosoideae....
tree above a small stream. Two nests were even built onto a concrete bridge in Gabon's Lopé National Park
Lopé National Park
Lopé National Park is a national park in central Gabon. Although the terrain is mostly rain forest, in the north the park contains the last remnants of grass savannas created in Central Africa during the last Ice Age, 15,000 years ago. It was the first protected area in Gabon when the Lopé-Okanda...
. The male and female rockfowl work equally on the nest's construction, and it can take two to three months to build one, though in some extreme cases it takes more than a year. The nest itself is a half-cup constructed of dry mud with grass fibers and dead leaves mixed in, often with the plant matter sticking out of the nest's walls. It is either built onto the rock surface or, in some cases, is built more like a retaining wall across the opening of a small rock fissure. Nests are built at least away 1 metres (3.3 ft) from each other, and in some cases up to 5 metres (16.4 ft). The nest is normally 30 to 40 cm (11.8 to 15.7 in) thick, though the nest is uneven in its construction and one nest was 140 centimetres (55.1 in) thick. It is about 290 centimetres (114.2 in) wide and 400 centimetres (157.5 in) long and weighs about 3 kilograms (6.6 lb). However, nest sizes do have a large degree of variability. After the mud dries, it becomes a very hard structure. The inside of the nest is lined with rootlets and thin strips of grass.
One to three eggs, normally two, are laid, with the second egg being laid between 24 and 48 hours after the first. The eggs are variable in coloration and can be a light yellow-brown with dark brown blotches, creamy white with dark brown or grey blotches, or pale grey with brown mottling. The eggs weigh about 15.2 gram (0.536164223997702 oz) and have an average size of 40.5 millimetres (1.6 in) by 27.5 millimetres (1.1 in). The rockfowl begins to incubate
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
after both eggs are laid. The time the rockfowl spends incubating varies greatly, though it is mostly for less than five minutes at a time with nearly two hours between sessions. Both the male and female rockfowl incubate. When the incubating bird's mate comes, it gives a brief call that causes the incubating bird to leave the nest. In the two days prior to hatching, the adult rockfowl prods at the eggs, sometimes with food in its beak. Incubation lasts for 21 to 24 days. When the infants hatch, they hatch about a day apart. The adult rockfowl quickly remove the eggshell fragments from the nest. The newborn weighs only 12 gram (0.423287545261344 oz) after hatching, but it quickly gains weight. The eyes open and the tail begins to grow on the fifth day. During the first couple of days, food is brought to the nestlings three to six times an hour, peaking in the evening. Begging nestlings expose their beak and gape to their parent, though they do not make a sound. The second-hatched nestling often fails to gain weight and dies, and there is evidence suggesting that the adults cannibalize the remains. For the first ten days after hatching, one adult rockfowl stays and guards the nestlings while the other collects food; despite this, nests have been destroyed by chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s and drills
Drill (mammal)
The Drill is a primate of the family Cercopithecidae , closely related to the Baboons and even more closely to the Mandrill.-Description:...
. The chicks leave the nest after 24 days. Infanticide has been recorded in this species, with rockfowl killing other rockfowl's young. In one case, a second pair of rockfowl moved onto a nest after killing the first pair's nestlings.
Relationship with humans
In Cameroon, the Grey-necked Rockfowl is respected by the indigenous peoples and, in some cases, even feared. It is known by many names to the indigenous peoples of Nigeria, with most of the translating to "bird of the rocks" or "fowl of the stream". Hunters sheltering in the rockfowl's nesting caves have been known to kill and eat adult rockfowl, though it is generally thought to be too small to eat and is left for children to hunt. In the 1950s and 1960s, western zoos desired this species, leading to a large demand to collect the rockfowl for display. British conservationist and author Gerald DurrellGerald Durrell
Gerald "Gerry" Malcolm Durrell, OBE was a naturalist, zookeeper, conservationist, author and television presenter...
made this species a target on two of his trips to Cameroon, which he describes in The Bafut Beagles
The Bafut Beagles
The Bafut Beagles by British naturalist Gerald Durrell tells the story of Durrell's collecting expedition to the Cameroons, made in 1949, with Kenneth Smith....
and A Zoo in My Luggage
A Zoo in My Luggage
A Zoo in My Luggage by British naturalist Gerald Durrell is the story of Durrell's 1957 animal collecting trip to British Cameroon, the northwestern corner of present day Cameroon. First published in 1960, it is one of a half-dozen books about animal collecting trips that Durrell wrote....
. The trade of this species is non-existent today, and, as the zoo population did not sustain itself despite sporadic breeding, the last captive rockfowl died at the Frankfurt Zoo in 2009. The Grey-necked Rockfowl has been depicted on numerous postage stamps from Cameroon and Nigeria, as well as stamps from Benin and Togo, where it does not live. It is considered one of the most difficult species of bird to see in the wild. The Grey-necked Rockfowl is a symbol for both conservation and ecotourism efforts in its range. This species is considered one of the five most desirable birds in Africa by ornithologists.
Conservation
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
due to habitat destruction, its isolated populations, collection of adults, predation, and a low breeding success rate. Its habitat is being destroyed to create large agricultural fields and cocoa plantations, as well as for logging and slash-and-burn agriculture. Due to the highly specialized requirements for its habitat, its population is very fragmented, and the species is believed to be naturally rare. Competition for its nesting sites is a result of these strict requirements and can lead to infanticide. Its estimated population is between 2,500 and 10,000 individuals, though it is believed that the population is at the lower end of the estimate. However, due to the inaccessibility of some parts of its range, it is also possible that this species is more common than believed. The population of some of these colonies is reaching the minimum levels needed for long-term viability. It also falls victim to spring traps set for mammals by hunters. However, a more serious threat to its numbers was the widespread collection of rockfowl for display in zoos in the 1950s and 1960s. There is a risk that it will be negatively affected by ecotourism due to disturbances in its daily routine if proper viewing procedures are not followed.
Cameroon is the only nation with a national law protecting this species. This law prohibits killing the rockfowl, though it can be captured with a proper permit. International trading of the Grey-necked Rockfowl is governed under CITES Appendix I, meaning that legal trading of this species is only authorized in extraordinary circumstances. In 2006 BirdLife International
BirdLife International
BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...
drafted an international action plan to provide strategies for protecting this species. This plan focused on surveying the remaining habitat, raising awareness amongst the local populace, and limiting the continued destruction of its habitat.
This rockfowl is protected in some of the areas in which it lives by national parks. Additionally, there seems to be little habitat destruction in Gabon and on Bioko as the locations in these places in which the rockfowl lives is believed to be too inaccessible for future human development. Recent surveys have also discovered new populations of the Grey-necked Rockfowl.