From Living the Scientific Life blog in the USA:
World’s Largest Bird Was a Glider
Discovered decades ago and formally described in 1980, Argentavis magnificens is the largest bird known. It lived six million years ago during the Miocene period throughout Argentina. It is nearly the size of a Cessna 152 light aircraft, with a 23-foot (7-meter) wing span and weighing approximately 150-pounds (70-kilograms). However, even though this bird’s muscles were well-developed, they still were not sufficient to generate enough lift for the giant bird to leave the ground. So how did this, the largest of all birds, fly?
Paleontologists have scratched their collective heads over this question for decades, although at least a few of them suspected that the bird soared.
“Takeoff capability is the limiting factor for the size of flying birds, and Argentavis almost reached the upper limit,” said Sankar Chatterjee, a professor of geosciences and curator of paleontology at the Museum of Texas Tech University, and lead author of the newly published paper. …
To carry out this research, the scientists used flight simulation software to learn more about the ancient bird’s flight parameters by providing it with the dimensions of the bird’s bones. This analysis revealed that Argentavis magnificens, similar to most large soaring birds, was too large to sustain powered flight, but could soar efficiently, reaching speeds of up to 67kph (41mph) under the right conditions.
Apparently, Argentavis relied on updrafts in the foothills of the Andes, known as thermals, which are columns of heated air that are deflected upward over a ridge or a cliff. …
Analysis of the region’s ancient climate suggests that thermals were present on most days. Thus, the bird probably spent most of its time gliding and foraging for prey, such as rabbits and hares, which it would have swallowed whole with its formidable beak.
“Its jaw mechanics were not suited for tearing flesh from carcasses, as in vultures, nor for tearing prey animals apart for swallowing, as in eagles and owls,” said co-author Kenneth Campbell, of the Natural History Museum of Los Angeles County.
The great kori bustard, Ardeotis tardi, is the heaviest modern flying bird weighing approximately 40-pounds (18-kilograms) and the wandering albatross, Diomedea exulans, has the longest wingspan at over 10-feet (3-meters).
The study appears in the Proceedings of the National Academy of Sciences.
See also here.
I have a problem with the “rabbits and hares” sentence in this really interesting article, as they did not live in Argentina during the Miocene. There were unrelated South American rodents then, somewhat like maras of today, looking a bit like hares and rabbits.
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