Kenai test blog afblijven

The shoebill (Balaeniceps rex), also known as the whale-headed stork, and shoe-billed stork, is a large long-legged wading 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 pelicans and herons in the Pelecaniformes. The adult is mainly grey while the juveniles are more brown. It lives in tropical East Africa in large swamps from South Sudan to Zambia.

Taxonomy

[edit]Molecular studies have found the hamerkop to be the closest relative of the shoebill.

The shoebill may have been known to Ancient Egyptians[3] but was not classified 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.[4][5][6] The genus name comes from the Latin words balaena "whale", and caput "head", abbreviated to -ceps in compound words.[7] Alternative common names are whalebill,[8] shoe-billed stork and whale-headed stork.[9]

Traditionally considered as 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". Based on osteological evidence, the suggestion of a pelecaniform affinity was made in 1957 by Patricia Cottam.[10] 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.[11] In 2003, the shoebill was again suggested as closer to the pelicans (based on anatomical comparisons)[12] or the herons (based on biochemical evidence).[13] A 2008 DNA study reinforces their membership among the Pelecaniformes.[14]

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.[15][16][17] It has been suggested that the enigmatic African fossil bird Eremopezus have features resembling those of the shoebill and the secretary bird.[18]

Shoebill skull

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.[9] 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.[19]

Voice

[edit]

The shoebill is normally silent, but they perform bill-clattering displays at the nest.[9] 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).[19]

Flight pattern

[edit]

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).[19] Long flights of the shoebill are rare, and only a few flights beyond its minimum foraging distance of 20 m (66 ft) have been recorded.