TERATORNIS: THE DEATH BIRD

Teratornis merriami (Merriam's Teratorn) was a huge North American teratorn, with a wingspan of around 3.5 to 3.8 meters (11 to 12 feet) and a wing area of 17.5 square meters, standing an estimated 75 cm tall and weighing about 15 kg. It was somewhat larger than the extant Andean Condor and nearly two times as heavy as the California Condor. A closely related genus, Aiolornis, was about 40% larger and lived at an earlier time; it was formerly known 

as Teratornis incredibilis, but is distinct enough to be placed in its own genus.T. merriami is the best-known of the teratorns. A large number of fossil and subfossil bones, representing more than 100 individuals, have been found in locations in California, southern Nevada, Arizona, and Florida, though most are from the Californian La Brea Tar Pits. All remains but one Early Pleistocenepartial skeleton from the Leisey Shell Pit near Charlotte Harbor, Florida (which may represent a different species or a subspecies) date from the Late Pleistocene, with the youngest remains dating from the Pleistocene-Holocene boundary.The finger bones are fused as in all modern birds; however, part of the index finger forms a shelf which aided in bearing the load of long and stout primaries, which enabled the bird to utilize strong upcurrents. The legs were similar to an Andean Condor's, but stouter, and the feet were able to hold prey items for tearing off pieces, but not able to exert a very forceful grip such as in birds of prey. Its wing loading was not much larger than a Californian Condor's, and Merriam's Teratorn should have been able to take off by simply jumping and beating its wings under most circumstances. (Campbell & Tonni, 1983). Indeed, it seems to have been better adapted for that than for utilizing a short run into the wind from an elevated location as condors do, as its legs are proportionally smaller and its stride less than in condors (Fisher, 1945).T. merriami generally lived in a manner similar to condors, although its larger bill suggests that it was a more active predator. Prey up to the size of a small rabbit would probably have been swallowed more or less whole, while carrion would have been fed on in a manner similar to that of condors or vultures. The large number of finds in the La Brea Tar Pits were usually considered to be from teratorns which were attracted by Pleistocene megafauna that became stuck in the viscous asphalt trying to drink from pools of water that gathered on the surface and died, with the teratorns subsequently falling victim to the sticky deposits too. Merriam's Teratorn probably played an important role in opening up the body cavities of carcasses for smaller birds like eagles and ravens which are also known to have frequented the locality, as mammalian predators, being unable to fly, could hardly reach most carcasses without getting mired in the asphalt themselves.