The shoebill (Balaeniceps rex), also known as the whale-headed stork, whalebill, and shoe-billed stork, is a large long-legged wading bird. It is named for 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 browner. It lives in tropical East Africa in large swamps from South Sudan to Zambia.

Taxonomy

thumb|left|alt=hamerkop|Molecular studies have found the [[hamerkop to be the closest relative of the shoebill.]]

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 English traveler 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 'whale' and / 'head'. Other common names are whalebill, shoe-billed stork, and whale-headed stork.

Traditionally considered as allied with the storks (Ciconiiformes), 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 (based on anatomical comparisons) or the herons (based on biochemical evidence). 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. The enigmatic African fossil bird Eremopezus has been suggested to have features resembling those of the shoebill and the secretary bird.

Description

alt=photograph|left|thumb|Shoebill

The shoebill is a tall bird, with a typical height range of , with some specimens reaching as much as . Length from tail to beak can range from , and wingspan is . Weight has reportedly ranged from . A male typically weighs around and is larger than a typical female of . When they are first hatched, 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. The shoebill is nonmigratory, but 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<!-- Adding "desert" here is redundant. --> 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.

Exceptionally for a bird this large, the shoebill often stands and perches on floating vegetation, making it 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. The shoebill, being solitary, forages 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, but 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 are snatched up during the strike and spilled out from the edges of the mandibles. The activity of hippopotamuses may inadvertently benefit the shoebill, as submerged hippos occasionally force fish to the surface.

Diet

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), African lungfish (Protopterus annectens), and Senegal bichir (Polypterus senegalus), various Tilapia species and catfish, the latter mainly in the genus Clarias. Other prey eaten by this species has included frogs, watersnakes, Nile monitors (Varanus niloticus), and baby crocodiles. More rarely, small turtles, snails, rodents, small waterfowl, and carrion reportedly have been eaten.

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. In the Bangweulu Swamps of Zambia, fish eaten by this species are commonly in the range of . The main prey items fed to young by the parents were the catfish Clarias gariepinus, (syn. C. mossambicus) and long watersnakes. They are docile with humans and show no threatening behavior. Researchers were able to observe a bird on its nest at a close distance – within . Shoebills are often kept in zoos, but breeding is rarely reported. Shoebills have bred successfully at Pairi Daiza in Belgium and at Tampa's Lowry Park Zoo in Florida.

Beginning in 2014 and with various interspersed surges of attention since then, the shoebill has become the subject of internet memes, in part due to its intimidating appearance and its tendency to stand still for long periods of time. One such example is a video of a shoebill standing in the rain whilst staring into the camera. These memes have since also appeared on the social media platform TikTok, bringing a comparatively unknown species of bird into popular culture. The shoebill also inspired the design of the Loftwing birds in the 2011 game The Legend of Zelda: Skyward Sword.

Status and conservation

Its population is estimated to be between and , the majority of which live in swamps in South Sudan, Uganda, eastern Democratic Republic of the Congo, and Zambia. Also, a viable population is in the Malagarasi wetlands in Tanzania. BirdLife International has classified it as Vulnerable with the main threats being habitat destruction, disturbance, and hunting. The bird is listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Habitat destruction and degradation, hunting, disturbance, and illegal capture are all contributing factors to the decline of this species. Agriculture cultivation and pastures for cattle have also caused significant habitat loss. Indigenous communities that surround shoebill habitats capture their eggs and chicks for human consumption and for trade. Frequent fires in southern Sudan and deliberate fires for grazing access contribute to habitat loss. Some swamps in Sudan are being drained for construction of a canal to control nearby waterways, causing more habitat loss.