Large grey, stork-like waterbird with a fantastically unique bill.
The Shoebill stork's most prominent feature is an enormous bill, which ends in a sharp curved hook and is said to resemble a wooden shoe. Shoebills stand 110 to 140 cm (43 to 55 in.); males are taller than females and have longer bills. Their stilt-like black legs end in feet characterized by extremely long toes.
Shoebill or whale-headed storks are endemic to Africa and inhabit the east-central part of the continent. The main populations are found in southern Sudan (mainly in the White Nile Sudd), the wetlands of northern Uganda and western Tanzania and the Bangweulu swamp of northeastern Zambia. Smaller populations occupy eastern Zaire and Rwanda. This bird's range usually coincides with that of papyrus and lungfish.
Biogeographic Regions: ethiopian (Native )
Balaeniceps rex is widely but very locally distributed in large swamps from South Sudan to Zambia. Approximate national estimates proposed by T. Dodman in litt. (2002) to Wetlands International (2002) are: South Sudan: c. 5,000 (50-80% of the total population [Briggs 2007]), Uganda: 100-150, (but possibly over 200 [Briggs 2007]), western Tanzania: 100-500 (this figure also proposed by Dinesen and Baker 2006), Zambia: <500 (though a later estimate of 1,760 with 1,296 in the Bangweulu Swamps alone is provided by Roxburgh and Buchanan 2010), Democratic Republic of Congo DRC: <1,000, Central African Republic (irregular), Rwanda: <50 and Ethiopia: <50. In 1997, the population was estimated to be 12,000-15,000 individuals (Rose and Scott 1997), but a more recent review makes a conservative estimate of 5,000-8,000 individuals (T. Dodman in litt. 2002 to Wetlands International 2002). This figure may prove too low, depending on research into the South Sudan populations (T. Dodman in litt. 2002 to Wetlands International 2002). An estimate of 3,830 birds was given for the Sudd (including areas of Zeraf Reserve) by Fay et al. (2007). A total population of less than 10,000 individuals is supported by a literature review in which the extent of certain wetland habitats was found to have been significantly overestimated by previous studies. Surveys in September-October 2005 support the suggestion that there are a few hundred individuals in the Malagarasi region of Tanzania (Briggs 2007). There is little doubt that the species is declining in Tanzania, Zambia and Rwanda, with declines perhaps in Uganda as well, and the species may be more threatened than available information suggests (L. Dinesen in litt. 2007).
Central Africa: Albertine Rift Valley and surroundings from Sudan to Zambia.
Large, somewhat frightful looking birds, shoebill storks stand 110 to 140 cm tall. Males are larger than females and have longer bills. The plumage is slaty blue-grey overall with a darker grey head. The primaries are black-tipped and secondaries have a greenish tint. The underparts are a lighter shade of grey. Adult breeding plumage does not differ from non-breeding plumage. On the back of the head is a small tuft of feathers that can erect in a crest. A newly hatched shoebill stork is covered in silvery-grey silky down and juveniles are a slightly darker shade of grey than adults. The bill is the most prominent feature of shoebill storks and resembles a wooden shoe. It is an enormous structure ending in a sharp, curved hook. The color of the bill is yellowish with blotchy dark spots. The mandibles have sharp edges that aid in capturing and eating prey. The eyes are large and yellowish or grayish-white in color. The legs are long and blackish. The toes are extremely long and completely divided with no webbing between them.
Range length: 110 to 140 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Shoebill storks inhabit freshwater swamps and extensive, dense marshes. 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.
Habitat Regions: tropical ; saltwater or marine
Wetlands: marsh ; swamp
Habitat and Ecology
Shoebill storks are inhabitants of freshwater swamps and extensive dense marshes throughout east-central Africa. Especially large populations of Shoebills are found in the Sudd of southern Sudan, northernUganda, western Tanzania and Zambia’s Bangweulu swamp.
Movements and dispersal
Mostly sedentary, with some movements (to find optimal feeding habitat)
Shoebill storks spend most of their time foraging in aquatic environments. The main part of their carnivorous diet consists of lungfish (Protopterus), bichirs (Polypterus), catfish, tilapia (Tilapia) and watersnakes. On occasion, they will also consume frogs, monitor lizards, turtles, young crocodiles, mollusks and carrion. The most suitable area for catching prey is one with shallow water and tall vegetation to camouflage the bird as it stalks prey. If the water is deep, a firm, floating platform of vegetation must be present in order to hunt.
The two mechanisms by which shoebill storks hunt are "stand and wait" and "wade and walk slowly." When a prey item is spotted, shoebill storks will begin the "collapse". The head and neck quickly stretch forward into the water causing the bird to over-balance and collapse forwards and downwards. After a collapse, a shoebill stork cannot immediately perform a second collapse. It must regain its balance and start from the standing position again. Along with the prey, a mouthful of vegetation is also collected. In order to expel the vegetation, shoebill storks sway their heads from side to side while keeping hold of the prey. Before swallowing, the prey is usually decapitated.
Animal Foods: amphibians; reptiles; fish; carrion ; mollusks
Primary Diet: carnivore (Eats terrestrial vertebrates, Piscivore )
Shoebill storks are important predators in the swamps and marshes where they live.
There are few predators of adult shoebill storks. Young and eggs may be taken by nest predators, but shoebill storks aggressively defend their young and build nests in areas inaccessible to many predators.
Predator: prey includes lungfish, catfish, tilapia and water snakes.
Life History and Behavior
Shoebill storks are usually silent, but will often participate in bill-clattering, a behavior characteristic of true storks. Adults will often do this when greeting each other at the nest, but young shoebills also perform the bill-clatter. Adults will also make a whining or "mooing" noise and young will make a hiccupping noise especially when begging for food.
The principal senses used during hunting are vision and hearing. In order to facilitate binocular vision, shoebill storks hold their heads and bills vertically downward against the breast.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Important wetland predators, Shoebill storks feed primarily on fishes such as lungfish, catfish, tilapia and water snakes. These stealthy hunters stand still or walk slowly through the water, then “collapse” forward and downward to snatch prey from just beneath the surface.
Shoebills form monogamous pairs and aggressively defend their breeding territories. Each pair constructs a large ground nest from grasses and other vegetation located on a small island or mass of floating vegetation. Although two eggs are laid, a pair is typically able to rear only a single chick each year.
Shoebill storks live to almost 36 years in the wild.
Status: wild: 35.7 (high) years.
Status: captivity: 35.7 years.
Status: captivity: 36.0 years.
Lifespan, longevity, and ageing
Shoebill storks form monogamous pairs for breeding.
Mating System: monogamous
Shoebill storks are solitary breeders and have territories measuring approximately 3 square kilometers. In the breeding season, these birds are very territorial and will defend the nest against any predators or competitors. Breeding time varies depending on location, but usually coincides with the start of the dry season. The reproductive cycle from nest building to fledging spans a period of 6 to 7 months. An area with a 3 meter diameter is trampled and cleared for the nest. The nest is located on either a small island or on a mass of floating vegetation. Nesting material, such as grass, is weaved on the ground, forming a large structure of about 1 meter in diameter. One to three, normally two, flaky whitish eggs are laid. However, by the end of the breeding cycle usually only one chick remains due to predation or food availability. The incubation period is about 30 days. After hatching, adult shoebill storks must feed the chicks regurgitated food at least 1 to 3 times per day and up to 5 to 6 times per day as the chick grows older. Parents hold out food to the chicks, which must feed themselves.
Breeding interval: Shoebill storks breed once yearly.
Range eggs per season: 1 to 3.
Average time to hatching: 30 days.
Average fledging age: 95 days.
Average time to independence: 125 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Shoebill storks are monogamous breeders and both parents participate in every aspect of nest building, incubation, and chick rearing. Egg-watering is a behavior that has been recorded on many occasions and that is also observed in true storks. In order to keep the eggs cool, the adult shoebill will get a mouthful of water and pour it over the nest. It will also get mouthfuls of wet grass to place around the eggs and will roll and turn over the eggs with its feet or bill. The dousing behavior and also shading will continue after the eggs hatch until the feathers of the chicks are fully developed.
The development of shoebill storks is a slow process compared to most other birds. Feathers do not fully develop until about 60 days and the birds fledge at 95 days. However, the young cannot fly until about 105 to 112 days. Parents continue to feed the young for about one month after fledging. After this point, young shoebill storks are totally independent of their parents.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
Evolution and Systematics
The beak of the shoebill stork efficiently probes and scoops mud to search for prey thanks to its hooked, shoe-like shape.
"The shoebill stork or whalebird lives in the papyrus swamps of the Upper White Nile and East Africa. Its main food is lungfish, for which it probes in the mud with its grotesque hooked bill, which may be up to 20 cm long. The bill is also used as a scoop to catch frogs and other small vertebrates." (Foy and Oxford Scientific Films 1982:151)
Learn more about this functional adaptation.
There have been many estimates of shoebill stork populations, but the most accurate is 11,000-15,000 birds over the entire range. Since populations of shoebill storks are scattered and most are inaccessible to humans (or nearly so) for much of the year, it is hard to get a reliable number. The IUCN rates shoebill storks as "Lower risk - near threatened". They are also listed in Appendix II of CITES. They are protected by law in Sudan, the Central African Republic, Uganda, Rwanda, Zaire and Zambia, and included in Class A of the African Convention of Nature and Natural Resources. Local folklore also protects shoebill storks and native people are taught to respect and even fear these birds.
Shoebill storks are most threatened by habitat destruction. They have specific habitat needs for nesting and foraging and their swamps and marshes are being rapidly converted to agricultural land and cattle grazing. Fishermen disturb the shoebill's habitat, especially their feeding areas. Another cause for concern is the zoo trade. The demand for shoebill storks in zoos is very high. They sell for US $10,000-$20,000 making them the most expensive birds in the zoo trade. This encourages native people to capture and sell these birds to zoos, thus reducing wild populations. There have been few accounts of shoebill storks breeding in captivity. If they do breed, the young imprint on the zookeepers and will not go on to breed themselves when they reach adulthood.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: vulnerable
IUCN Red List Assessment
Red List Category
Red List Criteria
IUCN Red List Status: VULNERABLE
There is little doubt that the species is declining in Tanzania, Zambia and Rwanda, with declines perhaps in Uganda as well, and the species may be more threatened than available information suggests (L. Dinesen in litt. 2007 in BirdLife International 2011).
Widespread but rare, Shoebills are estimated to have a world population of 5,000 – 8,000. Their wetland habitats are being rapidly converted to agricultural land. In addition, these unusual birds demand such high prices in the zoo trade that native people are capturing and selling them to zoos around the world.
CITES Appendix II. A Single Species Conservation Action Plan is being developed in 2012, including a stakeholder workshop, with representatives of all range states. Steps are being taken in South Sudan to understand the population better and improve the status of protected areas. Several key shoebill sites are designated Ramsar sites in South Sudan, Uganda, Tanzania and Zambia.
Conservation Actions Proposed
Agreed conservation actions for the species will be developed in 2012 and provided in the Shoebill Single Species Action Plan. Identify key areas for monitoring and conduct regular surveys. Select important areas for protection. Reduce disturbance and establish buffer zones in protected areas (L. Dinesen in litt. 2007). Enforce legislation in protected areas (L. Dinesen in litt. 2007). Create community-based environmental awareness programmes focussed on generating shoebill-pride to discourage hunting. Encourage further development of ecotourism based around this species. Investigate the potential occurrence of seasonal movements (Briggs 2007). Monitor rates of habitat conversion across its range. Re-submit the proposal to upgrade the species to CITES Appendix I, and implement trade control. Determine the Sudd swamps population size and trend (T. Dodman in litt. 2002 to Wetlands International 2002), and refine the national and global population estimates. Assess the viability of the population in Gambella, Ethiopia, an area under high pressure from agricultural developments.
Relevance to Humans and Ecosystems
There are no known adverse effects of shoebill storks on humans.
Shoebill storks are caught and sold for food. The native people also can receive large amounts of money from selling captured shoebill storks to zoos. They also bring in money through tourism because many people go to Africa on river excursions to look at wildlife.
Positive Impacts: food ; ecotourism
The shoebill (Balaeniceps rex) also known as whalehead or shoe-billed stork, is a very large stork-like bird. It derives its name from its massive shoe-shaped bill. Although it has a somewhat stork-like overall form and has previously been classified in the order Ciconiiformes, its true affiliations with other living birds is ambiguous. Some authorities now reclassify it with the Pelecaniformes. The adult is mainly grey while the juveniles are browner. It lives in tropical east Africa in large swamps from Sudan to Zambia.
Taxonomy and systematics
The shoebill was only classified in the 19th century when some skins were brought to Europe. It was not until years later that live specimens reached the scientific community. However, the bird was known to both ancient Egyptians and Arabs. Traditionally allied with the storks (Ciconiiformes), 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 (based on anatomical comparisons) or the herons (based on biochemical evidence; Hagey et al., 2002). A recent DNA study suggests they are part of the Pelecaniformes.
The dispute has turned out to be mainly one of where to draw the boundary between Ciconiiformes and Pelecaniformes, or whether to draw it at all. Since cormorants and relatives are probably not actually Pelecaniformes, a solution adopted by some modern authors is to merge the "core" Pelecaniformes with the Ciconiiformes. The shoebill and the hammerkop (Scopus umbretta) are the "missing links" that connect pelicans and storks, and including the pelican lineage in the Ciconiiformes expresses this more adequately than other treatments do.
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.
The shoebill is a tall bird, with a typical height range of 110 to 140 cm (43 to 55 in) and some specimens reaching as much as 152 cm (60 in). Length from tail to beak can range from 100 to 140 cm (39 to 55 in) and wingspan is 230 to 260 cm (7 ft 7 in to 8 ft 6 in). Weight has reportedly ranged from 4 to 7 kg (8.8 to 15.4 lb). A male will weigh on average around 5.6 kg (12 lb) and is larger than a typical female of 4.9 kg (11 lb). The signature feature of the species is its huge, bulbous bill, which is straw-coloured with erratic greyish markings. The exposed culmen (or the measurement along the top of the upper mandible) is 18.8 to 24 cm (7.4 to 9.4 in). The sharp edges in the mandibles help the shoebill to decapitate their prey and also to discard any vegetation after prey has been caught. 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 21.7 to 25.5 cm (8.5 to 10.0 in). The shoebill's feet are exceptionally large, with the middle toe reaching 16.8 to 18.5 cm (6.6 to 7.3 in) 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 58.8 to 78 cm (23.1 to 30.7 in), and well-adapted to soaring.
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 (Vultur gryphus). When flushed, shoebills usually try to fly no more than 100 to 500 m (330 to 1,640 ft) from their prior location. Long flights of the shoebill are rare, and only a few flights beyond its minimum foraging distance of 20 m (66 ft) have been captured.
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.
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.
Distribution and habitat
The shoebill is distributed in freshwater swamps of central tropical Africa, from southern 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 adjacent areas of the 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. The shoebill is non-migratory with limited seasonal movements due to habitat changes, food availability and disturbance by humans.
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 remain still for long periods, resulting in repeated 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 (Ardea goliath) is also known to stand on aquatic vegetation. Shoebills typically feed in muddy waters and, being solitary birds, forage at a minimum distance of 20 m (66 ft) 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 are successful in yielding prey. Frequently water and vegetation is snatched up during the strike and is spilled out from the edges of the mandibles. Occasionally, the activity of hippopotamus may inadvertently benefit the shoebill, as the huge mammals occasionally force fish to the surface of the water while they are submerged.
Shoebills are largely piscivorous but are assured predators of a considerable range of wetland vertebrates. Preferred prey species have reportedly included marbled lungfish (Protopterus aethiopicus) and Senegal bichir (Polypterus senegalus) as well as 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 (Varanus niloticus) and baby crocodiles. More rarely, turtles, snails, rodents and small waterfowl have reportedly been eaten. There exists a single report of shoebills feeding on lechwe (Kobus leche) calves, although this would need confirmation. Given its sharp-edged beak, huge bill and wide gape, the shoebill can hunt large prey, often targeting prey bigger than other large wading birds. Fish eaten by this species are commonly in the range of 15 to 50 cm (5.9 to 19.7 in) long and weigh around 500 g (1.1 lb), though lungfish of as much as 1 m (3.3 ft) have been attacked. Snakes preyed upon are commonly from 50 to 60 cm (20 to 24 in) long. In the Bangweulu Swamps of Zambia, the main prey items fed to young by the parents consisted of the catfish Clarias gariepinus (syn. C. mossambicus) and water snakes. In Uganda, lungfish and catfish were mainly fed to the young.
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 2 to 4 km2 (0.77 to 1.54 sq mi) 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 end of wet season in order to hatch around the beginning of the following wet season. Both parents engage in building the nest on floating platform, after clearing out an area of approximately 3 m (9.8 ft) across. The large, flattish nesting platform is often partially submerged in water and can be as much as 3 m (9.8 ft) deep. The nest itself is about 1 to 1.7 m (3.3 to 5.6 ft) across. Both the nest and platform are made of aquatic vegetation. In Sudan, the nests apparently were able to support the weight of an adult man, although this was not the case in Zambia. From one to three white eggs are laid. These eggs measure 80 to 90 mm (3.1 to 3.5 in) high by 56 to 61 mm (2.2 to 2.4 in) and weigh around 164 g (5.8 oz). Incubation lasts for approximately 30 days. Both parents actively brood, shade, guard and feed the nestling, though the females are perhaps slightly more attentive. 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 are intended as back-ups in case the eldest 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.
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 (Leptoptilos crumeniferus).
Status and conservation
The population is estimated at between 5,000 and 8,000 individuals, the majority of which live in swamps in Sudan, Uganda, eastern Democratic Republic of the Congo, and Zambia. BirdLife International has classified it as Vulnerable with the main threats being habitat destruction, disturbance and hunting.
Relationship to humans
This species is considered to be one of the five most desirable birds in Africa by ornithologists. There are Egyptian images depicting the shoebill, while the Arabs referred to the bird as abu markub, which means one with a shoe, a reference to the bird's distinctive bill.
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