The Bridger flyway, a component of the regional Rocky Mountain Flyway, is the largest known concentration of migratory Golden Eagles in the U.S with a long-term average annual count of 1,200 to 1,500 birds. It also attracts many other migrating raptors, with 18 species recorded since HawkWatch International (HWI) began monitoring the flight in 1991. Overall, combined-species counts typically range between 2,000 and 3,500 migrants per fall season.
Visit the HawkWatch International website for more information.
Observers monitor the Bridger migration daily from the beginning of September through the end of October each year. October is the peak activity period for both Golden and Bald Eagles, with Rough-legged Hawk activity mostly confined to the latter half of October. In contrast, the migrations of a few other species, such as Ospreys, Broad-winged Hawks, and Swainson's Hawks, are generally confined to September. For most other species, however, activity begins to pick up markedly in mid-September and generally peaks during the period spanning the last 10 days of September and first 10 days of October. Weather permitting, late September and early October are therefore the most productive times for visiting the site to see many species, with mid-October the best time for seeing lots of eagles. Peak daily activity periods vary with weather conditions, but generally extend from late morning to mid-afternoon.