The Thunderbird of North American native legend bears much similarity to the roc, a giant eagle- or vulture-like bird with supernatural powers in old-world lore.1 Although there are regional variations of the legend, Native Americans are in agreement that the Thunderbird is a magical animal that protects them from evil; it rides in on a storm, its eyes flashing with lightning and its extraordinary wings roaring like thunder, at times emitting a flute-like sound.2

The three most predominant legends emanated from the Winnebago Indians of the northern Midwest and Plains states, the Passamaquoddy Indians of the Northeast, and the Quillayute Indians of the Pacific Northwest. The Winnebagos believed that the Thunderbird could assume human form, as a birdman. To the Passamaquoddy tribe, the Thunderbird was a man who could change himself to a giant bird with supernatural powers and ties to the divine world. The Quillayutes described an enormous winged creature with feathers the size of a canoe paddle that could grab whales from the ocean, take them back to their mountain caves, and eat them. There was a prehistoric creature that fits that description — the pterosaur — that reportedly had a wing span of up to 33 feet, though it is not classified as a bird but as an ancient dinosaur that could fly.2

Cryptozoologists differentiate the Thunderbird of folklore from the “thunderbird” of the animal kingdom: They define a thunderbird as an abnormally large North American predatory bird that can bear some resemblance to the legendary Thunderbird, but they would also include a giant owl in the same category. The animal thunderbird can also appear to be a huge condor with eagle features. Because this creature is seen in the same areas always at the same time of the year, cryptozoologists consider the possibility that it could be a rare giant migratory bird much like the now-extinct teratorn (var. teratomis Merriami), a huge scavenger bird, or perhaps a giant bat or pterosaur, a dinosaur relative.1

The legendary Thunderbird’s wingspan is estimated to be between 15 and 20 feet, although there have been reports indicating it is far larger than that. Its height at rest appears to be between 4 and 8 feet. It is capable of swooping down and carrying off dogs and children.3 There are no photographic records of the Thunderbird, although in the late 1800s a photograph of six men standing near a huge bird that had been killed and hung on the wall of a barn reputedly circulated in the Arizona territory before being lost. Alleged copies of the photo were published before but have since disappeared.2,3,4

Sightings continue to be reported, for example, in Australia, Mexico, and Norway, with a major portion of them from Pennsylvania. Several people — from different parts of the state — reported seeing a bird they described as being the size of a small airplane as recently as 2001. There are earlier reports of children being abducted and later dropped, and there was a report attributed to the Associated Press in the Cincinnati Enquirer of the abduction of a beagle in Kentucky in September 1977. The Boston Globe is said to have run a story in July 1977 about the abduction and subsequent release of a 10-year old boy in Illinois.5

In the Franklin Mountain range in El Paso, Texas, is a startling red clay formation in the shape of a Thunderbird.6

There is a strong similarity between Thunderbird and Mothman, and some believe they are related.7

1. http://www.newanimal.org/thunderbird.htm
2. http://www.mysteriousworld.com/Journal/1999/Autumn/Thunderbird/
3. http://www.angelfire.com/pq/cryptozoologix/thunderbird.html
4. http://www.rense.com/general3/thun.htm
5. http://paranormal.about.com/library/weekly/aa100801b.htm
6. http://www.lostdestinations.com/tbird.htm (includes photos)
7. http://www.boudillion.com/Mothman