Shoebill
The shoebill, also known as the whale-headed stork, whalebill, and shoe-billed stork, is a large long-legged wading bird. Its name comes from its enormous shoe-shaped bill. It has a somewhat stork-like overall form and was previously classified as a stork in the order Ciconiiformes; but genetic evidence places it with pelicans and herons in the Pelecaniformes. Adults are mainly grey while juveniles are more brown. It lives in tropical East Africa in large swamps from South Sudan to Zambia.
Taxonomy
The shoebill may have been known to Ancient Egyptians but was not classified by Europeans until the 19th century, after skins and eventually live specimens were brought to Europe. John Gould very briefly described it in 1850 from the skin of a specimen collected on the upper White Nile by the English traveller Mansfield Parkyns. Gould provided a more detailed description in the following year. He placed the species in its own genus Balaeniceps and coined the binomial name Balaeniceps rex, from Latin balaena 'whale' and caput/ceps 'head'. Other common names are whalebill, shoe-billed stork, and whale-headed stork.Traditionally considered as allied with the storks, it was retained there in the Sibley-Ahlquist taxonomy which grouped many unrelated taxa into the Ciconiiformes. Based on osteological evidence, the suggestion of a pelecaniform affinity was made in 1957 by Patricia Cottam. 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. In 2003, the shoebill was again suggested as closer to the pelicans or the herons. A 2008 DNA study reinforces their membership among the Pelecaniformes.
So far, two fossilized relatives of the Shoebill have been described: Goliathia from the Early Oligocene of Egypt and Paludiavis from the Late Miocene of Pakistan and Tunisia. It has been suggested that the enigmatic African fossil bird Eremopezus have features resembling those of the shoebill and the secretary bird.
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 pinkish in color 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.
Voice
The shoebill is normally silent, but they perform bill-clattering displays at the nest. When engaging in these displays, adult birds have also been noted to utter a cow-like moo as well as high-pitched whines. Both nestlings and adults engage in bill-clattering during the nesting season as a means of communication. When young are begging for food, they call out with a sound uncannily like human hiccups. In one case, a flying adult bird was heard uttering hoarse croaks, apparently as a sign of aggression at a nearby marabou stork.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.File:Shoebill-uenozoo2008.ogv|thumb|alt=photograph|A shoebill at the Ueno Zoo, 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, and 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 often attracted to poorly oxygenated waters such as swamps, marshes, and bogs where fish frequently surface to breathe. They also seem to exhibit migratory behaviors based upon differences in the surface water level. Immature shoebills abandon nesting sites which increased in the surface water level whereas adult shoebills abandon nesting sites which decreased in surface water level. It is suggested that both adult and immature shoebills prefer nesting sites with similar surface water levels. 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, 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.File:Balaeniceps rex -Ueno Zoo, Tokyo, Japan-8a.jpg|thumb|right|alt=photograph|A shoebill standing at Ueno Zoo, Tokyo
Breeding
The solitary nature of shoebills extends to their breeding habits. Nests typically occur at less than three nests per square kilometre, unlike herons, cormorants, pelicans, and storks, which predominantly nest in colonies. The breeding pair of shoebills vigorously defends a territory of from conspecifics. In the extreme north and south of the species' range, nesting starts right after the rains end. In more central regions of the range, it may nest near the end of the wet season in order for the eggs to hatch around the beginning of the following wet season. Both parents engage in building the nest on a floating platform after clearing out an area of approximately across. The large, flattish nesting platform is often partially submerged in water and can be as much as deep. The nest itself is about wide. Both the nest and platform are made of aquatic vegetation. From one to three white eggs are laid. These eggs measure high by and weigh around. Incubation lasts for approximately 30 days. Both parents actively brood, shade, guard and feed the nestling, though the females are perhaps slightly more attentive. Shoebills use their mandibles to cool their eggs with water during days with high temperatures around. They fill their mandible once, swallow the water, and fill another mandible full of water before proceeding back to their nest where they pour out the water and regurgitate the previously swallowed water onto both the nest and eggs. Food items are regurgitated whole from the gullet straight into the bill of the young. Shoebills rarely raise more than one chick but will hatch more. The younger chicks usually die and function as "back-ups" in case the eldest chick dies or is weak. Fledging is reached at around 105 days and the young birds can fly well by 112 days. However, they are still fed for possibly a month or more after this. It will take the young shoebills three years before they become fully sexually mature.Shoebills are elusive when nesting, so cameras must be placed to observe them from afar to collect behavioral data. There is an advantage for birds that are early breeders, as the chicks are tended for a longer period.