They are considered servants of the Great Spirits of the World and live on lonely mountain peaks. As much as these monsters are feared, they are also revered by the people.
Some think that these thunderbirds are Pterandonon. These are a genus of Pterosaurs and include some of the largest flying reptiles the world has ever seen. And, with the abundance of fossilized remains of this specie in America, they may be the same species.
But it is strange because these flying lizards should have disappeared millions of years ago. But there is evidence that residents of the early North American region had multiple encounters with these giant birds from as close as 200 years ago.
Other evidence includes photographs from 1864, during the American Civil War, where a massive bird-like creature lies dead beneath the boots of six American soldiers. As for the latest story we know of, in 1977, three youngsters from Illinois were hunted by a creature that resembled a big bird and only stopped when it got one of the kids and flew off.