Some six million years ago, the mountains and pampas of what is now Argentina were shaded by the wings of the largest flying bird ever discovered, the condor-like Argentavis magnificens. Now researchers led by Sankar Chatterjee of Texas Tech University have analyzed its capabilities, feeding measurements into a computer program to simulate the great bird's flight, and concluded this 70-kg bird with a wingspan over six meters was probably as large as any flying bird could get. It was so large that, while an excellent glider, it could not take off from level ground. If it came down to the flatlands for prey, it probably needed to find a slight downslope into a headwind just to get airborne. While some researchers believe the bird was a scavenger, Chatterjee and his colleagues believe its skull and beak (over half a meter long!) were better suited for a hunter-killer lifestyle.
(Comment: This is one of those species we humans should be truly sad that we never got to observe in person. We don't know when it became extinct, but it was presumably long before the first humans appeared in that region. As to its lifestyle, almost all predators will scavenge when the opportunity presents itself. We recently discovered that even the ocean's apex predator, the orca, will scavenge. It seems reasonable that A. magnificens would take whatever it could find, living or dead. )