Shoebill
The shoebill also known as whalehead, whale-headed stork, or shoe-billed stork, is a very large stork-like bird. It derives its name from its enormous shoe-shaped bill. It has a somewhat stork-like overall form and has previously been classified with the storks in the order Ciconiiformes based on this morphology. However, genetic evidence places it with the Pelecaniformes. The adult is mainly grey while the juveniles are browner. It lives in tropical east Africa in large swamps from South Sudan to Zambia.
Taxonomy and systematics
The shoebill was known to both ancient Egyptians and Arabs, but was not classified until the 19th century, after skins and eventually live specimens were brought to Europe. John Gould described it in 1850, giving it the name Balaeniceps rex. The genus name comes from the Latin words balaena "whale", and caput "head", abbreviated to -ceps in compound words.Traditionally allied with the storks, it was retained there in the Sibley-Ahlquist taxonomy which lumped a massive number of unrelated taxa into their "Ciconiiformes". More recently, the shoebill has been considered to be closer to the pelicans or the herons. Microscopic analysis of eggshell structure by Konstantin Mikhailov in 1995 found that the eggshells of shoebills closely resembled those of other Pelecaniformes in having a covering of thick microglobular material over the crystalline shells. A recent DNA study reinforces their membership of the Pelecaniformes.
So far, two fossil relatives of the shoebill have been described: Goliathia from the early Oligocene of Egypt and Paludavis from the Early Miocene of the same country. It has been suggested that the enigmatic African fossil bird Eremopezus was a relative too, but the evidence for that is unconfirmed. All that is known of Eremopezus is that it was a very large, probably flightless bird with a flexible foot, allowing it to handle either vegetation or prey.
Description
The shoebill is a tall bird, with a typical height range of and some specimens reaching as much as. Length from tail to beak can range from and wingspan is. Weight has reportedly ranged from. A male will weigh on average around and is larger than a typical female of. The signature feature of the species is its huge, bulbous bill, which is straw-coloured with erratic greyish markings. The exposed culmen is, the third longest bill among extant birds after pelicans and large storks, and can outrival the pelicans in bill circumference, especially if the bill is considered as the hard, bony keratin portion. As in the pelicans, the upper mandible is strongly keeled, ending in a sharp nail. The dark coloured legs are fairly long, with a tarsus length of. The shoebill's feet are exceptionally large, with the middle toe reaching in length, likely assisting the species in its ability to stand on aquatic vegetation while hunting. The neck is relatively shorter and thicker than other long-legged wading birds such as herons and cranes. The wings are broad, with a wing chord length of, and well-adapted to soaring.The plumage of adult birds is blue-grey with darker slaty-grey flight feathers. The breast presents some elongated feathers, which have dark shafts. The juvenile has a similar plumage colour, but is a darker grey with a brown tinge. When they are first born, shoebills have a more modestly-sized bill, which is initially silvery-grey. The bill becomes more noticeably large when the chicks are 23 days old and becomes well developed by 43 days.
Flight pattern
Its wings are held flat while soaring and, as in the pelicans and the storks of the genus Leptoptilos, the shoebill flies with its neck retracted. Its flapping rate, at an estimated 150 flaps per minute, is one of the slowest of any bird, with the exception of the larger stork species. The pattern is alternating flapping and gliding cycles of approximately seven seconds each, putting its gliding distance somewhere between the larger storks and the Andean condor. When flushed, shoebills usually try to fly no more than. Long flights of the shoebill are rare, and only a few flights beyond its minimum foraging distance of have been recorded.Identification
At close range, it can be easily identified by its unique features. In flight, if its unique bill cannot be seen, the shoebill's silhouette resembles that of a stork or condor, but its feathers are a distinctive medium blue-grey. Also unusual, its tail is the same colour as its wings. Under poor viewing conditions, its size and wingspan can distinguish it from other birds in its habitat. Its legs, roughly the length of storks', extend straight back far past its tail when in flight. The wing to tail size cannot be used for identification; it is similar to those of several other birds., Tokyo,
Distribution and habitat
The shoebill is distributed in freshwater swamps of central tropical Africa, from southern Sudan and South Sudan through parts of eastern Congo, Rwanda, Uganda, western Tanzania and northern Zambia. The species is most numerous in the West Nile sub-region and South Sudan ; it is also significant in wetlands of Uganda and western Tanzania. More isolated records have been reported of shoebills in Kenya, the Central African Republic, northern Cameroon, south-western Ethiopia, Malawi. Vagrant strays to the Okavango Basin, Botswana and the upper Congo River have also been sighted. The distribution of this species seems to largely coincide with that of papyrus and lungfish. They are often found in areas of flood plain interspersed with undisturbed papyrus and reedbeds. When shoebill storks are in an area with deep water, a bed of floating vegetation is a requirement. They are also found where there is poorly oxygenated water. This causes the fish living in the water to surface for air more often, increasing the likelihood a shoebill stork will successfully capture it. The shoebill is non-migratory with limited seasonal movements due to habitat changes, food availability and disturbance by humans.Petroglyphs from Oued Djerat, eastern Algeria, show that the shoebill occurred during the Early Holocene much more to the north, in the wetlands that covered the present-day Sahara Desert at that time.
The shoebill occurs in extensive, dense freshwater marshes. Almost all wetlands that attract the species have undisturbed Cyperus papyrus and reed beds of Phragmites and Typha. Although their distribution largely seems to correspond with the distribution of papyrus in central Africa, the species seems to avoid pure papyrus swamps and is often attracted to areas with mixed vegetation. More rarely, the species has been seen foraging in rice fields and flooded plantations.
Behaviour and ecology
The shoebill is noted for its slow movements and tendency to stay still for long periods, resulting in descriptions of the species as "statue-like". They are quite sensitive to human disturbance and may abandon their nests if flushed by humans. However, while foraging, if dense vegetation stands between it and humans, this wader can be fairly tame. The shoebill is attracted to poorly oxygenated waters where fish frequently surface to breathe. Exceptionally for a bird this large, the shoebill often stands and perches on floating vegetation, making them appear somewhat like a giant jacana, although the similarly sized and occasionally sympatric Goliath heron is also known to stand on aquatic vegetation. Shoebills typically feed in muddy waters and, being solitary, forage at or more from one another even where relatively densely populated. This species stalks its prey patiently, in a slow and lurking fashion. While hunting, the shoebill strides very slowly and is frequently motionless. Unlike some other large waders, this species hunts entirely using vision and is not known to engage in tactile hunting. When prey is spotted, it launches a quick violent strike. However, depending on the size of the prey, handling time after the strike can exceed 10 minutes. Around 60% of strikes yield prey. Frequently water and vegetation is snatched up during the strike and is spilled out from the edges of the mandibles. The activity of hippopotamus may inadvertently benefit the shoebill, as submerged hippos occasionally force fish to the surface., Tokyo
Shoebills are largely piscivorous but are assured predators of a considerable range of wetland vertebrates. Preferred prey species have reportedly included marbled lungfish and Senegal bichir and various Tilapia species and catfish, the latter mainly in the genus Clarias. Other prey eaten by this species has included frogs, water snakes, Nile monitors and baby crocodiles. More rarely, turtles, snails, rodents and small waterfowl have reportedly been eaten. There is a single unconfirmed report of shoebills feeding on lechwe calves. Given its sharp-edged beak, huge bill and wide gape, the shoebill can hunt large prey, often targeting prey bigger than is taken by other large wading birds. Fish eaten by this species are commonly in the range of long and weigh around, though lungfish of as much as have been attacked. Snakes preyed upon are commonly from long. In the Bangweulu Swamps of Zambia, the main prey items fed to young by the parents were the catfish Clarias gariepinus and water snakes. In Uganda, lungfish and catfish were mainly fed to the young. The big beak is sometimes used to dig into pond-bottom mud to extract lungfish from their aestivation burrows.