Thunderbird reports in Montana
2 cases, best-documented first. Page 1 of 1.
We map claims, not creatures. A case is what some source says someone saw or heard, with the link to that source. It is not proof that anything was there, and a retelling counts once, not as a second sighting.

Thunderbird · Glacier National Park, Montana · 1927
The text reports that Piegan Indians believed Chief Mountain was the home of a Thunder Bird which caused thunder and lightning.

Thunderbird · Glacier National Park, Montana · 1934
The text recounts Blackfeet legends stating that Chief Mountain is the home of the Thunder Bird, a creature associated with storms and lightning.