Picathartes
Encyclopedia
The picathartes, rockfowl or bald crows are a small genus of two passerine
bird
species
forming the family Picathartidae found in the rain-forests of tropical west and central Africa
. They have unfeathered heads, and feed on insects and invertebrates picked from damp rocky areas. Both species are totally non-migratory
, being dependent on a specialised rocky jungle habitat.
s with crow-like
black bills, long neck, tail and legs. They weigh between 200–250 g (7.1–8.8 ). The strong feet and grey legs are adapted to terrestrial movement, and the family progresses through the forest with long bounds on the ground. The wings are long but are seldom used for long flights
. The plumage
is similar between the two species, with white breasts and bellies and darker (grey and grey-black) wings, backs and tails. The neck colour varies between the two species, giving the two species their individual names (Grey-necked and White-necked Picathartes). They also have bald heads with brightly coloured and patterned skin.
s, termite
s and ant
s, as well as millipede
s, centipede
s, earthworm
s and gastropods. Frog
s and lizard
s are also taken, but these are mostly fed to their chicks. Prey is taken both by foraging on the ground and in the trees. They will also forage in shallow flowing water for crabs. When foraging on the ground they move forward with hops and bounds, then pausing to search for prey. The longish bill is used to turn over leaves and seize prey, but the feet are never used for either. Both species will follow
swarms of ants in order to snatch prey fleeing the ants.
Both species of picathartes breed seasonally in the wet season
. Where an area experiences two wet seasons in a year they will breed twice in the year. Despite reports of cooperative breeding it is now thought that they are exclusively monogamous
, breeding in pairs. They are also commonly reported to be colonial
, and will breed in colonies of up to seven pairs, but solitary breeders and smaller colonies of just two pairs are more common. The nest
is made of mud attached to a cave roof or overhanging rock on a cliff. The nest is a cup like structure of dried leaves, twigs and plant fibres set into dried mud. Two eggs are laid, 24 to 48 hours apart. Both parents participate in incubating
the eggs, each taking 12 hour shifts before being relieved by their partner. It takes around 20 days for the eggs to hatch. Picathartes hatchlings are altricial
at hatching, almost naked (a few feathers are present on the crown and back) and helpless. The chicks take around 25 days to fledge
.
Both species are listed as Vulnerable
to extinction on the IUCN Red List
.
A possible third species may exist in Uganda
, in the vicinity of the Kasinga Channel, linking Lake Edward
with Lake George
.
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...
bird
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...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
forming the family Picathartidae found in the rain-forests of tropical west and central Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. They have unfeathered heads, and feed on insects and invertebrates picked from damp rocky areas. Both species are totally non-migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, being dependent on a specialised rocky jungle habitat.
Description
The picathartes are large (33 – long) passerinePasserine
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...
s with crow-like
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...
black bills, long neck, tail and legs. They weigh between 200–250 g (7.1–8.8 ). The strong feet and grey legs are adapted to terrestrial movement, and the family progresses through the forest with long bounds on the ground. The wings are long but are seldom used for long flights
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
. The plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
is similar between the two species, with white breasts and bellies and darker (grey and grey-black) wings, backs and tails. The neck colour varies between the two species, giving the two species their individual names (Grey-necked and White-necked Picathartes). They also have bald heads with brightly coloured and patterned skin.
Taxonomy
The taxonomic position of the genus and its two species has been confusing. At various times, it has been grouped with the babblers, flycatchers, starlings, crows and others before being placed in a family of its own. Serle in 1952 thought it resembled the Asian genus Eupetes while Sibley used egg-albumin protein similarity, determined by electrophoresis, to suggest that it belonged to the Timaliidae. Storr Olson revived the idea that it was related to Eupetes in 1979. A molecular sequence based study suggests that it may indeed be closely related to the crows.Behaviour
The picathartes are generalised feeders, taking a wide range of invertebrate prey. Prey items include a range of insects, particularly beetleBeetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s and ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s, as well as millipede
Millipede
Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...
s, centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...
s, earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...
s and gastropods. Frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s and lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s are also taken, but these are mostly fed to their chicks. Prey is taken both by foraging on the ground and in the trees. They will also forage in shallow flowing water for crabs. When foraging on the ground they move forward with hops and bounds, then pausing to search for prey. The longish bill is used to turn over leaves and seize prey, but the feet are never used for either. Both species will follow
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...
swarms of ants in order to snatch prey fleeing the ants.
Both species of picathartes breed seasonally in the wet season
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
. Where an area experiences two wet seasons in a year they will breed twice in the year. Despite reports of cooperative breeding it is now thought that they are exclusively monogamous
Monogamy
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...
, breeding in pairs. They are also commonly reported to be colonial
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in close proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony...
, and will breed in colonies of up to seven pairs, but solitary breeders and smaller colonies of just two pairs are more common. The nest
Bird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
is made of mud attached to a cave roof or overhanging rock on a cliff. The nest is a cup like structure of dried leaves, twigs and plant fibres set into dried mud. Two eggs are laid, 24 to 48 hours apart. Both parents participate in incubating
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...
the eggs, each taking 12 hour shifts before being relieved by their partner. It takes around 20 days for the eggs to hatch. Picathartes hatchlings are altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
at hatching, almost naked (a few feathers are present on the crown and back) and helpless. The chicks take around 25 days to fledge
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
.
Both species are listed 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:...
to extinction on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
.
Species
- White-necked RockfowlWhite-necked RockfowlThe 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...
, Picathartes gymnocephalus - Grey-necked RockfowlGrey-necked RockfowlThe Grey-necked Rockfowl 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...
, Picathartes oreas
A possible third species may exist in Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...
, in the vicinity of the Kasinga Channel, linking Lake Edward
Lake Edward
Lake Edward or Edward Nyanza is the smallest of the African Great Lakes. It is located in the western Great Rift Valley, on the border between the Democratic Republic of the Congo and Uganda, with its northern shore a few kilometres south of the Equator...
with Lake George
Lake George (Uganda)
Lake George or Lake Dweru is a lake in Uganda. It covers a total surface area of 250 km² and is a part of Africa's Great Lakes system but is not itself considered one of the Great Lakes. Like the other lakes in the region it was named after a member of the British royal family, in this case...
.