Tuesday, July 2, 2013

As the nestling develops, its plumage begins to resemble

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.[16] 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.[19] Sony VPCS136EC Battery The Grey-necked Rockfowl is a relatively silent species.[16] It has been known to give a quiet, one to two second long, hissing "wheet" call several times at intervals of about four seconds.[16] To give this call, the rockfowl opens its beak and inflates its throat.[16] When bringing food to their nests, the adults give one or two "peep"s.[16] Sony VPCS138EC Battery

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.[16] 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.[20] Sony VPCS139GC Battery In Nigeria, it is only found in the nation's southeastern corner near the coast and the Cameroon border.[3] The species is widespread in southwestern Cameroon, and this country is considered to be the species' stronghold.[21] It is found throughout Equatorial Guinea and into southwestern Gabon.[20] Additionally, the species resides in the southwestern forests of the island of Bioko in the Gulf of Guinea.[3] Sony VPCYA15EC Battery 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.[2][8] The Grey-necked Rockfowl's total range covers approximately 314,000square kilometres (121,000 sq mi).[20] Sony VPCYA16EC Battery It is found in undisturbed rain forests with closed canopies.[20] The Grey-necked Rockfowl prefers rugged terrain in these forests covered in large boulders, caves, and gorges.[16] Additionally, it often found near inselbergs and a source of water, either a river or a forest pool.[15] The understory of its forests has sparse undergrowth or open spaces but is covered in mosses, Sony VPCYA25EC Battery ferns, lianas, and epiphytes.[16] In southwestern Bioko it is found in low forests that receive nearly 10 metres (33 ft) of rain a year.[16] Bioko's habitat also has dense undergrowth and vertical gorges near a caldera.[16] The rockfowl's habitat is normally found between 450 and 2,100 metres (1,480 and 6,900 ft) above sea level, though it is lower in elevation on Bioko.[16] Sony VPCYA26EC Battery This species is non-migratory, and at one site in Cameroon the birds remained within 300 metres (980 ft) of their nesting site throughout the year.[22] It is capable of living near human activity, and one breeding site in Cameroon was located within 30 metres (98 ft) of a maize plot.[15] This and other recent observations suggest that the rockfowl has greater tolerance for degraded habitat than previously thought. Sony VPCYB15JC Battery This rockfowl usually lives either alone or in pairs, although small flocks of three to ten birds are not uncommon.[16] It normally moves through its habitat in a series of runs and long, springing hops on the ground and in low branches.[16] It uses its tail for balance while hopping and running.[15] When in a flock, rockfowl hop almost in unison.[22] Sony VPCYA17GH/R Battery In the unusual occurrences when the species does fly, it is fast and is capable of navigating through the trees and rocks well.[22] When it is standing still, the rockfowl has its tail down and its head looking up.[22] Typically, it silently evades any unusual movements in their forest.[23] However, if these birds know that they have been sighted, Sony VPCCW2S8E/W Battery they can become quite inquisitive and occasionally approach observers.[23] 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.[22] When this species is suspicious, it raises the small crown on its head and the ruff on its neck while uttering a muffled groan.[22] Sony VPCCW2Z1E/B Battery 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 liana-tangled areas or in caves away from the nests.[22] To scratch its head, the species lifts its foot over its head.[24] It bathes in small pools.[22] While its lifespan in the wild is unknown, it has lived up to 25 years in captivity. Sony VPCY11S1E Battery This species forages in the early morning or late afternoon either alone or in small groups in leaf litter and on dead tree trunks.[22] It is also known to leap upwards to grab prey on overhanging foliage.[22] It looks for its prey either by standing still and scanning the surrounding area or by tossing the leaf litter away with its beak.[22] Sony VPCY11S1E/S Battery It also frequently follows columns ofDorylus ants, feeding on the insects flushed by the ants.[20] It also is known to hunt in streams for crabs and fish.[14] It crushes snails with its beak and, if its prey struggles, smashes it against the ground.[22] While an uncommon occurrence, male rockfowl have been observed giving food to a female.[26] Sony VPCW1 Battery The Grey-necked Rockfowl feeds on a diverse range of invertebrates and small vertebrates, though plant matter does constitute a major part of its diet.[22][26] It is known to eat beetles, including weevils, rove beetles, and click beetles from the genusPsephus, butterflies, ants from the genera Dorylus and Pachycondyla, grasshoppers, Sony VPCW1E8R/BU Battery cockroaches from the family Blattidae, earwigs,caterpillars, ant-lions, silverfish, and earthworms.[22] Small lizards, frogs, snails, and slugs are also eaten, as are crabs from the genus Potamon, fruits, flower buds, mosses, and leaves.[22][26] Fish have also been identified as a prey item in Nigeria.[14] Sony VPCY11AGJ Battery At at least one nesting site, it relies heavily on the arthropods feeding on the bat guano near the cave for sustenance, while this behaviour has been reported to a lesser extent at other sites.[22][27] It is known to regurgitate what it has eaten in pellet form.[22] Overall, between 52 and 60 percent of the bird's diet is believed to be composed of animals.[26] Sony VPCY11AHJ Battery

Rove beetle larvae and ants were the most frequently eaten prey in a study in Nigeria.

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.[2] It is monogamous and therefore does not breed with rockfowl other than its mate.[22] Sony VPCY11AVJ Battery It is believed to breed cooperatively in Equatorial Guinea, as four different birds were observed feeding one nest.[28] The rockfowl's courtship displays are unknown.[22] The timing of the egg laying in a colony is not synchronized, leading to various stages of development of nestlings within the colony.[22] Sony VPCY11M1E Battery It has been suggested that this is to promote cooperative breeding.[28] The laying dates also vary by region, typically coinciding with a few weeks before the onset of the wet season;[28] in areas where the wet season is bimodal, two different breeding seasons occur.[2] However, in mountainous regions such as Mount Cameroon, Sony VPCY11S1E Battery it breeds during the dry season to avoid the frequent mists of the wet season.[14] 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, Sony VPCY11V9E Battery

a main one from October to December and a secondary one lasting from April to May.[29] In Equatorial Guinea, nesting occurs in mid-February.[28]

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.[22] Sony VPCY11V9E/S Battery Nests need to be built under an overhang to protect it from water, and the rock surface normally slopes forward slightly.[14] The nests are almost always found near water, which can be in the form of either streams or forest pools.[28] These streams, particularly those located at the base of a nesting cliff, help keep predators away from the nests.[20] Sony VPCY219FJ/S Battery Nests on rock surfaces are normally built 1.2 to 5.2 metres (3.9 to 17 ft) above the ground.[22] 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.[14] Two nests were even built onto a concrete bridge in Gabon's LopĂ© National Park.[30] Sony VPCY21AFJ Battery 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.[22] The nest itself is a half-cup constructed of dry mud with grass fibres and dead leaves mixed in, often with the plant matter sticking out of the nest's walls.[22] Sony VPCY21AGJ Battery 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.[22] Nests are built at least away 1 metre (3.3 ft) from each other, and in some cases up to 5 metres (16 ft).[28] The nest is normally 30 to 40 centimetres (12 to 16 in) thick, though the nest is uneven in its construction and one nest was 140 centimetres (55 in) thick.[22] Sony VPCY21AHJ Battery It is about 290 centimetres (110 in) wide and 400 centimetres (160 in) long and weighs about 3 kilograms (6.6 lb).[22] However, nest sizes do have a large degree of variability.[19] After the mud dries, it becomes a very hard structure.[22] The inside of the nest is lined with rootlets and thin strips of grass.[22] Sony VPCY21AVJ Battery One to three eggs, normally two, are laid, with the second egg being laid between 24 and 48 hours after the first.[20] 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.[22] The eggs weigh about 15.2 grams (0.54 oz) and have an average size of 40.5 millimetres (1.59 in) by 27.5 millimetres (1.08 in).[29] Sony VPCY21S1E/L Battery

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