Bald Eagle Surveys Document Long Term Trends
Bald eagle surveys conducted over the last two decades may show an increase in the number of bald eagles wintering along the Skagit River between Rockport and Newhalem. The Skagit Valley hosts one of the largest concentrations of this threatened bird of prey in the lower 48 states. The arrival of the eagles coincides with the spawning of salmon, whose carcasses are the birds major food source. Variations in chum salmon runs and weather patterns account for some fluctuations in census numbers. Resource managers are concerned that increasing recreational activities could seriously impact eagles. Baseline and long-term studies are necessary to detect long-term changes in eagle numbers.
Only a small proportion of the bald eagles wintering on the Skagit River feed between Marblemount and Newhalem. National Park Service biological surveys showed an interesting trend in that area during the first 10 years of the study. During the early 1980's little variability existed, with total sightings ranging from 125 to 139. However, beginning in the 1987-88 winter, total sightings ranged from 221 to 319. The percent of subadults also increased. Larger numbers of immature eagles are an indication of better breeding success up north, where they spend their summers, and may partially account for an increase in the abundance of bald eagles concentrated along the Skagit River each winter.
A complementary study began in 1984 with volunteers coordinated by the Forest Service documenting bald eagle nightroost activity. Data provided by these studies may support protection of eagle habitat in the Skagit Valley. They also will lead to habitat improvement projects for salmon and eagles, thus enhancing their survival. Signs were placed to help visitors learn about the eagle's life cycle, habits and special needs.
These surveys are fine examples of interagency cooperation between the USDA Forest Service, National Park Service, North Cascades Institute, Skagit Audubon, Wildcat Steelhead Club, Nature Conservancy (Skagit River Bald Eagle Natural Area) and many concerned volunteers.
Check out the Bald Eagle Counts. Skagit Bald Eagle Counts are compiled from the three simultaneous surveys that are done on Wednesdays from early December through February by National Park Service, Forest Service and the Nature Conservancy.
Last updated: August 11, 2017