Based on fossils discovered in 1983 during excavations for a new airport terminal, scientists have modeled the flight of the largest flying bird ever reported. Named Pelagornis sandersi, the extinct bird had a 6.4-meter wingspan -- double that of today’s largest fliers.
A bird’s flight ability depends on a balance between its body size and the lift forces generated by its wings. Researchers previously thought that wingspans wider than 5 meters made it impossible for flight. While this puts the new extinct bird above the theoretical limits for powered flight, computer models show it was capable of highly efficient gliding flight, according to a new study published in Proceedings of the National Academy of Sciences this week. "Science had made a rule about flight, and life found a way around it,” Daniel Ksepka from the Bruce Museum tells the Washington Post.
Giant seabirds in the prehistoric family Pelagornithidae are known for bony tooth-like protrusions along their bills and specialized wing bones. “Pelagornithids were like creatures out of a fantasy novel -- there is simply nothing like them around today,” Ksepka says in a news release. They occurred all over the globe for tens of millions of years, but vanished three million years ago. He adds: "Pelagornis sandersi could have traveled for extreme distances while crossing ocean waters in search of prey.” It likely stayed aloft for a week at a time, swooping down to snatch fish from the water.
Working from a fossil skull, wing bones, and leg bones discovered in 25-million to 28 million-year-old sediment at the Charleston International Airport in South Carolina, Ksepka extrapolated the bird’s body dimensions and then modeled possible flight styles, including flapping and gliding.
The largest fragment belonged to a humerus that would have been 94 centimeters long if complete, Science reports. From wingtip to wingtip, P. sandersi measured at least 6.4 meters. The wandering albatross, the world’s largest living bird, has a wingspan of 3.5 meters, and the giant, extinct South American condor, Argentavis magnificens, was right around 6 meters. Pictured here, a skeletal reconstruction of P. sandersi with a California condor (lower left) and royal albatross (lower right) for scale.
In 24 different computer simulations, Ksepka combined this wingspan with a range of various parameters, including body sizes and the ratio of wing length to breadth. Proportions of its weight-bearing bones suggest it weighed between 22 and 40 kilograms, and its feather length were estimated based on bone and feather lengths of living birds.
Ksepka concluded that P. sandersi was a highly efficient glider that soared at least as well as albatrosses, attaining high lift-to-drag ratios with fast glide speeds. On average, he tells Science, for every 1 meter the bird dropped while gliding, it moved forward 22 meters.
Getting aloft may have been more difficult, given its tiny legs. It probably took off by running down slopes into headwinds, he tells New Scientist. Nor do the simulations reveal how something so massive with such thin bones could land safely.
The new species was named after retired Charleston Museum curator Albert Sanders, who collected the fossil.
Images: Liz Bradford (top, bottom) & Daniel Ksepka (middle)