A close-up of a taxiderm shoebill's head, highlighting its extraordinary beak (left) and a vintage portrayal of a shoebill first published in 1901 (right) (© Dr Karl Shuker / public domain)
One of the bird world's oddest-looking species is unquestionably Balaeniceps rex, whose scientific name translates as 'whale-headed king' – but as its head bears little resemblance to a whale, this is a somewhat strange name, even for as strange a bird as Balaeniceps. Standing up to 5 ft tall, its general appearance is that of a large, round-shouldered stork with slaty blue-grey plumage and an untidy crest, but distinguishing it instantly from any genuine stork is its enormous, grotesque beak.
Roughly 8 in long, with a sharply hooked tip, this incongruous structure greatly resembles a clog-like shoe, earning Balaeniceps a much more apt and more commonly used name - shoebill. Similarly, the Arabs call this bird Abu-markub, 'Father of the shoe'.
Vintage illustration of the shoebill's head (top) and a shoebill skull readily demonstrating its beak's disproportionately huge size compared to the rest of its skull (bottom) (© Huub Veldhuijzen van Zanten/Naturalis Biodiversity Center – CC BY-SA 3.0 licence)
A peculiar but characteristic behavioural attribute of the shoebill is its tendency to stand perfectly still for lengthy periods of times. Recalling this, several years ago a correspondent informed me that when she was a child visiting her first zoo, she saw what she initially assumed to be a statue of some strange dinosaur-bird, because it was completely immobile. Fascinated, she stood and looked at it unsuspectingly for a time - until, without warning and in best Talos tradition (fans of the classic Ray Harryhausen film Jason and the Argonauts from 1963 will know exactly what I mean here!), this 'statue' slowly turned its head until it was staring directly at her! Its steely gaze peering down its huge beak into her face totally petrified the poor little girl, who was convinced that she was about to be torn apart and devoured!
Happily, the shoebill is in reality a shy, inoffensive species, inhabiting the relatively inaccessible papyrus marshes and floating swamps of the Upper Nile and its central East African tributaries, where it uses its massive beak to catch and extract prey such as fish, water snakes, and frogs (possibly even small mammals, and young crocodiles too) from the surrounding vegetation. It was once believed that its shoe-like shape was a specific adaptation for scooping lungfishes out of the mud, but as lungfishes do not form this species' principal diet, that idea seems unfounded - just as unfounded, it would appear, as many of the assumptions put forward over the years regarding this species' taxonomic affinity to other birds.
Section from an 1870s chromatolithograph depicting a pair of shoebills in their natural swampland habitat (public domain)
Science first became aware of the shoebill in the early 1840s. In his Expedition to Discover the Sources of the White Nile, in the Years 1840, 1841 (1849), German explorer Ferdinand Werne reported that on 15 December 1840 his party saw a remarkable bird that seemed to them to be as large as a young camel, with a huge pelican-like beak, but lacking the pelican's characteristic pouch. This was undoubtedly a shoebill; sadly, Werne was asleep at the time and his party was unwilling to wake him, so he never observed it himself.
Eight years later, however, German ornithologist-explorer Baron Johann W. von Müller was more fortunate, catching sight of two shoebills. Moreover, upon his return to base at Khartoum, Sudan, he saw a pair of dead specimens for sale offered by a slave-dealer. The price that he was asking was too high to interest Baron von Müller, but not long afterwards they were purchased by a traveller from Nottingham named Mansfield Parkyns, who brought them back to England when he returned with various other animal specimens collected during his African sojourn. These were studied by the eminent bird painter John Gould, who prepared a formal scientific description of the shoebill, presented on 14 January 1851 at a meeting of London's Zoological Society and published later that year in its Proceedings. And in 1860, Britain's first pair of living shoebills arrived at London Zoo, courtesy of Welsh traveller John Petherick.
Another pair of shoebills in their natural habitat, this time painted by okapi discoverer Sir Harry Johnston and published in 1902 (public domain)
Meanwhile, the controversy concerning this species' relationship to other birds had begun in earnest. Gould had classified it as an aberrant, long-legged pelican; but other ornithologists did not agree with that, and tended to ally it either with the herons or with the storks. Today, the shoebill is generally categorised as the sole living occupant of its own family, discrete from both the herons and the storks. The reason for the phenomenal difficulty in satisfactorily classifying this bird rests with its anatomy and behaviour, which embrace a perplexing potpourri of features drawn from at least three different bird families - and two different orders.
Powder-downs are pairs of strange feathers that are never shed, but perpetually fray at their tips to yield a powder that the bird rubs into its other feathers. Herons have three pairs, and the shoebill has a single pair, but storks have none. Also in common with herons, the shoebill's rear toe is held at the same level as its three forward-pointing toes (the rear toe is raised in storks); and when it flies, the shoebill tucks its head and neck backwards, like herons once again.
And a smile on the face of the shoebill? (photo by Sengkang - copyrighted free use)
Even so, whereas in herons the stapes (birds' only middle-ear bone) is primitive in form, avian evolutionist Dr Alan Feduccia showed that it has an identical derived shape in the storks and the shoebill (Nature, 21 April 1977). Also agreeing with the storks: the shoebill's middle toe is less than half the length of the tarsus (heel-bone), and it has no webbing between its toes (herons have a partial web between 2-3 of theirs). It displays the storks' beak-clattering behaviour too.
Yet as if all of this were not already sufficient to demonstrate the shoebill's transitional form and conduct, its skull exhibits certain features similar to those of a completely separate order of birds – Pelecaniformes, the pelicans. Furthermore, in true pelican style, it flies with its large beak resting on its breast. Indeed, in 1957 the detailed skeletal studies undertaken by former British Museum ornithologist Dr Patricia A. Cottam on the shoebill convinced her that Gould had been correct all along, that this enigmatic species really was most closely related to the pelicans. However, other researchers (notably Dr Joel Cracraft in the ornithological journal Auk, 1985) dismissed its similarities as examples of convergence, i.e. they reasoned that because the shoebill and the pelicans exist in similar habitats and have similar lifestyles, they have evolved into similar forms, even though they originate from separate ancestral stocks.
Then in February 1986 after having directly compared the shoebill's DNA with that of herons, storks, and pelicans, researchers Drs Charles G. Sibley and Jon E. Ahlquist announced in Scientific American that, contrary to all expectations, the shoebill's DNA most closely matched that of the pelicans! They published further data in support of their finds during the 1990s. In 2001, extensive research involving DNA hybridisation as well as nuclear and mitochondrial DNA sequence analyses by a team headed by Dr Marcel van Tuinen added further support for the pelicans, the shoebill, and another enigmatic species called the hammerhead or hamerkop Scopus umbretta being of monophyletic (common) origin.
Comparable results were also obtained from a comprehensive osteological study by Frankfurt-based ornithologist Dr Gerald Mayr, published in 2003. Modern studies thus offer persuasive evidence for believing, as Gould had proposed over 160 years ago, that the shoebill is basically an aberrant pelican, and that its cranial affinities with pelicans signify direct kinship rather than deceptive evolutionary convergence.
Shoebills – not singular storks but peculiar pelicans, relatively speaking; painting by Joseph Wolf, 1862 (public domain)
In recent years, the shoebill's classification has also attracted attention because the results of more detailed genetic comparisons (notably the extensive phylogenomic study by Dr Shannon J. Hackett and a large team of co-workers - Science, 12 July 2008), involving many different avian genera and families, have required taxonomists to carry out a major overhaul of the contents of the avian orders Ciconiiformes and Pelecaniformes. These changes can be summarised as follows.
Traditionally, Ciconiiformes has contained the following families: Ardeidae (herons, egrets, bitterns), Balaenicipitidae (shoebill), Scopidae (hammerhead), Ciconiidae (storks), Threskiornithidae (ibises and spoonbills), and Phoenicopteridae (flamingos). Pelecaniformes, meanwhile, has contained Phaethontidae (tropic-birds), Fregatidae (frigate-birds), Sulidae (gannets and boobies), Anhingidae (anhingas or darters), Phalacrocoracidae (cormorants and shags), and Pelecanidae (pelicans). However, modern genetic studies have shown fairly convincingly that Pelecaniformes is polyphyletic, i.e. its families do not all originate from a single common ancestor, but in reality seem to constitute three entirely separate evolutionary lineages. One of these lineages consists of the tropic-birds, which therefore are now housed within their own separate order, Phaethontiformes. A second lineage comprises the gannets and boobies, cormorants and shags, anhingas, and frigate-birds. So these have all been grouped together within their own new order too, Suliformes. This means that only one original family remains within Pelecaniformes – the pelicans, constituting a third separate lineage.
Facing up to some taxonomic tribulations (© Leyo/Wikipedia – CC BY-SA 3.0 licence)
However, genetic studies have also shown, somewhat unexpectedly, that within the order Ciconiiformes are certain families – namely, the herons, bitterns, and egrets; the shoebill; the hammerhead; and the ibises and spoonbills – that are more closely related to the pelicans than they are to the remaining ciconiiform families. In short, Ciconiiformes is also polyphyletic. Consequently, these pelican-allied families have now been removed from Ciconiiformes and placed alongside the pelican family within Pelecaniformes. And the flamingos have been allocated their own separate order, Phoenicopteriformes. This means that the only family now remaining in Ciconiiformes is the storks.
Having said that, however, some taxonomists believe that the New World vultures' family, Cathartidae, and the extinct teratorns' family, Teratornithidae, are actually more closely related to the storks than to the Old World vultures or any other birds of prey. Consequently, they have duly included Cathartidae and Teratornithidae alongside the stork family Ciconiidae in Ciconiiformes. Meanwhile, the shoebill is nowadays back to where it began when first formally described during the 1800s, as a member of the pelican order. However, it is seen, along with the hammerhead, as a taxonomic link between Pelecaniformes and Ciconiiformes.
Shoebill showing off its powerful pinions (© Pelican/Wikipedia – CC BY-SA 2.0 licence)
Even the shoebill's fossil antecedents have stimulated taxonomic turmoil. Until its reclassification in 1980 by Dr Pierce Brodkorb as an ancestral shoebill (based upon the finding of a tarsometatarsus that revealed this taxonomic affinity), Goliathia andrewsi had been classed as an aberrant heron. It was first described in 1930 by Hungarian palaeontologist Dr Kálmán Lambrecht, following the discovery of an ulna bone dating from the early Oligocene, which had been obtained in the Jebel Qatrani Formation within Egypt's Fayum Province. The only other widely-accepted fossil relative of the shoebill is Paludavis richae, with remains found in Tunisia and Pakistan, but these are more recent, from the Miocene.
Of cryptozoological interest is the shoebill's implication in a very curious case of mistaken identity. From time to time, reports emerge from various remote regions of Central Africa describing alleged sightings of large, macabre-looking creatures soaring through the skies and bearing an impressive resemblance to those long-extinct flying reptilians, the pterosaurs. However, it is more than likely that many of these involve shoebills, as noted by zoologist Dr Maurice Burton (Animals, 18 February 1964 – click here to read more about his comments on ShukerNature) and subsequently explored in greater detail by me within my books In Search of Prehistoric Survivors (1995) and Still In Search Of Prehistoric Survivors (2016) – click here for coverage on ShukerNature of my books' documentation. There is no doubt that this strange bird has a distinctly prehistoric appearance, especially when viewed in flight, and anyone unfamiliar with the striking spectacle of its huge, 8.5-ft wingspan and giant beak could certainly be forgiven for thinking that they had spied an aerial anachronism, a cryptic creature supposedly dead for more than 64 million years.
This ShukerNature blog article is adapted from my book The Menagerie of Marvels.
Awe-inspiring sight of a shoebill in flight (© Tom Tarrant/Wikipedia – CC BY SA.30 licence)
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