Like modern condors, the six-million-year-old Argentavis magnificens—the largest bird known to have taken flight—may have relied on updrafts and thermals to soar above what is now Argentina. Based on fossils, researchers estimated that Argentavis, with its seven-meter wingspan, would have lacked the pectoral power to fly by flapping alone but was well suited to gliding. It could have circled within a thermal in tight 200-foot-wide spirals as it scanned for prey, according to a paper published online this week by Proceedings of the National Academy of Sciences USA.