fossil record THE BEST GUIDES FOR SERIOUS TWITCHERS Available at bookstores nationwide The Hoatzin’sdrifting Namibian connection apart
Ask any group of birders he story begins in 2003, heading to South America for when an extinct bird their first visit to that continent called Namibiavis senutae to name the species on their wasT described from fossil bones wishlists and it is a safe bet that found at Arrisdrif on the lower AFRICA the Hoatzin Opisthocomus hoa- Orange River in southern Nami
zin will, without exception, fea bia, not far inland from the river’s Brazil up a considerable distance One of South America’s most ture in the top ten. This iconic mouth. Namibiavis occurred in from their native range. We iconic birds, the Hoatzin may in SOUTH Hoazinavis Namibia bird inhabits swamps and flood this area around 17 million years AMERICA fossil location know for a fact that this hap fact have African roots. Namibiavis ed lowland forests, and has been ago (MYA) and, when its fossils Atlantic fossil location pens: there are eyewitness ac a source of fascination to orni were first described, it was thought Ocean counts of creatures as large as prevailing at the time would Also in thologists ever since it was first to belong to the order contain- Hoatzin distribution boa constrictors dispersing to have made a westward rafting e-book described to science. The chicks ing modern-day cranes, crakes distant islands in this fashion. journey more likely than an possess claws on the digits of and rails. However, when the fos Atlantic Ocean was nar The rafting hypothesis is par eastward one. their wings, a feature not found sil bones were subsequently re- rower than it is now but still ticularly plausible for hoatzins If the sequence of events in any other living species but examined by a team led by Gerald a formidable barrier. It is ex as lowland riverine habitats hypothesised by these re Acommon in early birds such as Mayr, it became apparent that the tremely unlikely that hoat are ideal for the formation of searchers is correct, hoatzins Archaeopteryx. The chicks’ claws earlier assessment was incorrect zins could have flown across; natural rafts. It is quite pos evolved in Africa. At some and the bizarre appearance of and Nambiavis was, in fact, a spe modern Hoatzins are weak sible that a few early hoatzins point before 23 MYA, they the adults collectively imbue the cies of hoatzin. The same team of flyers, and fossils suggest that found themselves acciden dispersed by raft across the Hoatzin with an air of primitive researchers also identified another their ancestors were equally tal passengers on a large raft Atlantic to South America ness, evoking images of a time extinct hoatzin that occurred mediocre in this department. well stocked with plants, and and then existed on both con when the distinction between around 23 MYA in what is now It is a realistic proposition for survived long enough to float tinents for at least six million reptile and bird was much more south-east Brazil, and they named strong flyers to occasionally across an Atlantic Ocean nar years. They subsequently went blurred than it is now. it Hoazinavis lacustris. cross the Atlantic (as southern rower than today’s. extinct in their ancestral Afri It is perhaps fitting that the taxo Africa and South America were African birders discovered This leaves the question can homeland, leaving South nomic affinities of this exceedingly once both part of the supercontin when a Black Skimmer, which of the direction in which the America as the sole refuge odd bird have been the source ent Gondwana, but were complete occurs in North and South ancestral hoatzins made the for the hoatzin lineage. It is of more head-scratching among ly separated by around 100 MYA. America, turned up near crossing – eastwards from an arresting thought that the ornithologists than those of nearly This was long before the appear Cape Town late last year), but South America to Africa or species sometimes described any other species. The birds with ance of any group of birds to the notion of something as in the opposite direction? Al as the world’s strangest bird Also in e-book which the Hoatzin has at vari which the hoatzins could even ungainly as a hoatzin flapping though Hoazinavis (the fossil may have had an African ous times been putatively linked distantly be related and the pos across several thousand kilo hoatzin from Brazil) existed origin and very likely reached make for a long list, and include sibility of them existing before the metres of ocean is beyond the some six million years before the New World by sea. Join our Struik Nature Club to break up of Gondwana can safely limits of credulity. ANDREW McKECHNIE groups as diverse as rails, bustards, Namibiavis, Mayr and his be the fi rst to fi nd out about cuckoos and mousebirds. While be ruled out. So these findings of Instead, Mayr and his col colleagues believe that hoat- the distant family tree of the Hoat two extinct species on either side leagues argued, hoatzins zins actually arose in Africa, Reference: Mayr, G., Alvaren- our new releases, author zin still remains far from clear, re of the Atlantic Ocean immediately made the crossing by raft. An and dispersed from there to ga, H. and Mourer-Chauviré, talks and great giveaways. cent research has lifted the lid on raise intriguing questions: how did imals trapped on large float South America. The research C. (2011) ‘Out of Africa: fossils Visit www.randomstruik.co.za a surprising chapter in its evolu hoatzins cross the Atlantic, and in ing mats of vegetation washed ers came to this conclusion on shed light on the origin of the and click on Nature Club , and tionary history, revealing that it is which direction did they do it? out to sea from river mouths the basis of evidence suggest hoatzin, an iconic Neotropic you could win a copy of Sasol not quite as quintessentially South At the time when early hoatzins can – if the currents and ing that the ocean currents bird.’ Naturwissenschaften Birds of Southern Africa. pete oxford (2) American as we might think. somehow crossed it, the South winds are favourable – land and atmospheric conditions 98: 961–966.
34 african birdlife january/february 2013
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