Balaeniceps rexshoebill

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Geographic Range

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.

Habitat

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.

Physical Description

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.

  • Sexual Dimorphism
  • sexes alike
  • Range length
    110 to 140 cm
    43.31 to 55.12 in

Reproduction

Shoebill storks form monogamous pairs for breeding.

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

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

Lifespan/Longevity

Shoebill storks live to almost 36 years in the wild.

Behavior

Shoebill storks are and are never found in groups. Only when food is in short supply will shoebill storks forage near each other. Often, the male and female of a breeding pair will forage on opposite sides of their territory. Adults use gular-fluttering in order to keep cool.

Shoebill storks are non-migratory as long as good foraging conditions exist. However, in some areas of their range, they will make seasonal movements between nesting and feeding zones. Shoebill storks soar on thermals and are often seen soaring above their territory during the day. In flight, the neck is retracted. Shoebill storks are very docile with humans. Researchers studying these birds have been able to come within 6 feet of a shoebill stork on its nest. The shoebill stork will not threaten humans, but will only stare right back at them.

Communication and Perception

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.

Food Habits

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

Predation

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.

Ecosystem Roles

Shoebill storks are important predators in the swamps and marshes where they live.

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

There are no known adverse effects of shoebill storks on humans.

Conservation Status

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.

Other Comments

The taxonomy of shoebill storks has been marked by debate over which birds are their closest relatives. The powder-down patches and syrinx link it to herons (Ciconiiformes) while the tongue morphology shows it is most like hammerkops (Scopidae). The shoebill stork's behavior, especially bill clattering, and the morphology of the stapes suggest relationship to true storks (Ciconiiformes). Previous biochemical analysis placed shoebill storks as a subfamily of Pelecanidae. Currently they are placed in their own family and order, Balaenicipitiformes.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Angie Steffen (author), University of Michigan-Ann Arbor, Robert Payne (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Buxton, C. 1977. The Shoebill Story. Black Lechwe, 12(3): 6-17.

Buxton, L., J. Slater, L. Brown. 1978. The breeding behavior of the shoebill or whale-haeded stork Balaeniceps rex in the Bangweulu Swamps, Zambia. East African Wildlife Journal, 16: 201-220.

DelHoyo, J., A. Elliott, J. Sargatal (eds.). 1992. Handbook of the Birds of the World. Barcelona: Birdlife/Lynx Edicions.

Feduccia, A. 1977. The Whalebill is a stork. Nature, 266: 719-720.

Guillet, A. 1979. Aspects of the foraging behaviour of the shoebill. Ostrich, 50: 252-255.

Guillet, A. 1978. Distribution and conservation of the shoebill (Balaeniceps rex) in the southern Sudan. Biological Conservation, 13: 39-49.

Hancock, J., J. Kushlan, M. Kahl. 1992. Storks, Ibises and Spoonbills of the World. New York: Academic Press.