Each year, South Dakota participates in an effort to count eagles in the lower 48 states. The effort is primarily directed at bald eagles, but counters also keep track of golden eagles. Although bald eagles winter at many locations in South Dakota, most congregate on the open waters of the Missouri River, particularly below the four mainstem dams. Because of this pattern, South Dakota's four standard eagle survey routes were established in 1984 on Lake Oahe, Lake Sharpe, Lake Francis Case, and the lower Missouri River to the state border.

The Midwinter Survey is not an exact count, but it helps in identifying trends in bald eagle winter distribution. High counts in South Dakota sometimes indicate that surrounding wetlands are frozen, forcing bald eagles to the only open water available. High counts might also indicate mild winter weather in the state, since severe winters may force bald eagles farther south. This cooperative effort is an informative and important conservation tool.

To learn more about the national Midwinter Bald Eagle Survey effort, visit the Snake River Field Station site.