So,, for what its worth.,,,,
The history channel is doing a documentory on a sighting of an actual thunderbird. Its on right now.
Not to sound dumb but what is an actual thunderbird. I assumed it was the Air Force plane and the word came from the American Indians
It was the shape shifting giant bird of the Hyda, in the B.C./Washington area. A particular tribe lays claim to being the shape-shifters of old. There are stories of the sounds of crashing surf during a storm are actually the wings of the great Thunderbird fighting the Orca out at sea.
That's as much as I can remember, and if you find anything contrary in your google search, please correct me.