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Cenozoic World

Ancient American Bird was a Glider

Edited from BBC News, 2 July 2007. Updated 19 December 2017

The largest bird known to have taken to the skies would have been a remarkable glider. A North American team studied the flight abilities of Argentavis magnificens, which lived six million years ago in Argentina.

With its seven metre-long wingspan, the animal must have been an expert at riding thermals and updrafts. But, according to the team behind research in 2007 when talking to the PNAS journal (Proceedings of the National Academy of Sciences), at 70kg it may have struggled to get airborne by flapping its wings.

Instead, the group believed, Argentavis probably used the same technique to get into the air as that employed by modern hang-gliders - by running downhill or by launching from a perch to pick up speed and lift. But once it was on a thermal, it could easily rise up a kilometre or three without any flapping of its wings - a free ride, just circling. Then at the top, the bird could simply glide to the next thermal and in this way it could certainly travel three hundred-and-twenty kilometres a day, according to Professor Sankar Chatterjee, curator of palaeontology at the Museum of Texas Tech University in Lubbock, USA.

On the runway

Professor Chatterjee and colleagues estimated the flight parameters of fossil Argentavis bones and plugged the information into computer flight models. The results indicated that the bird - which could have rivalled some light aeroplanes for size - would probably not have had the muscle power to lift itself into the air from a standing take-off or even maintain continuous flapping flight. However, Argentavis certainly had all the makings of a high-performance glider.

Its giant wings would have extracted the maximum energy from rising air forced up by the slopes of the rocky Andes or the warming atmosphere above the grassy pampas, the Argentine plains.

Like an albatross or a hanglider, Argentavis needed a little sloping surface; and he needed to run a bit, and a headwind would have helped. Using this trick he could have taken off but after that he wouldn't have needed to do much flapping of the wings.

All sizes

Writing in PNAS, the team added: 'Because the Argentavis fossils are found between the foothills of the Andes and the pampas, it is likely that it primarily used slope-soaring over the windward slopes of the Andes and thermal-soaring over the open pampas.'

With its powerful beak and big clawed feet, Argentavis would have made a fearsome predator, swooping down to snatch unsuspecting rodents. The kori bustard (Ardeotis kori) has a claim to being the heaviest modern flying bird at about 18kg (40lbs).

The wandering albatross (Diomedea exulans) is widely recognised as the modern avian with the longest wingspan, at more than 3m (10ft). The biggest flying animals known to science were pterosaurs. The flying reptiles which lived more than 65 million years ago had wingspans exceeding 10m (30ft).

Graphic of Argentavis
The biggest-known flying bird - Argentavis magnificens - which soared over the terrain between the foothills of the Andres and the pampas

Map of fossil location
Giant Bird - Fossil Finds
  • 1 & 2. Andalhuala Formation, near Catamarca in Valle de Santa Maria, Andes foothills
  • 3. Epecuen Formation, Carhue
  • 4. Salinas Grandes de Hidalgo in the Argentine pampas


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