Thunderbird Glacier is a glacier in Montana’s Glacier National Park, below Thunderbird Mountain on the east side of the Continental Divide at about 8,000 feet above sea level. By 2005, it had shrunk into numerous ice patches totaling 58 acres, leaving it more than 33 percent smaller than it was in 1966. Its decline reflects the broader reduction of high-country ice features that has become a notable part of the park’s modern landscape.