Bald Eagle De-Listing
On June 28, 2007, the bald eagle was removed from the U.S. list of threatened and endangered species. After nearly disappearing from most of the United States decades ago, wildlife enthusiasts are celebrating the eagle’s recovery. Now that this keystone predator has been restored to historical levels, it will be important to monitor the eagle’s impact on marine birds.
In the Puget Sound Georgia Basin, bald eagles prey on common murres, cormorants, grebes, gulls, herons, loons, scoters and other marine birds, many of which are in decline. Ecosystems are structured by a labyrinth of connections and the story is never as simple as predator up / prey down.
Are declining marine birds really being eaten by eagles or is the presence of eagles causing marine birds to move further off shore where they are not being counted? What role do salmon declines play in the marine bird decline story? When eagles move from coastal areas to rivers to eat spawning salmon, predation pressure eases on marine birds in coastal areas. Some biologists have suggested a close association between the strength of the region’s salmon runs and marine bird abundance. If this is the case, salmon declines could indirectly be contributing to marine bird declines.
To get the knowledge we need to ultimately have healthy salmon, eagle, and marine bird populations in the region, the SeaDoc Society is supporting Rob Butler of the Pacific Wildlife Foundation and Dan Esler of Simon Frasier University to study the complex relationships between eagles, salmon and marine birds in the Puget Sound Georgia Basin region. Preliminary results indicate that eagle numbers are lowest during the summer breeding season and greatest in February when herring spawn, suggesting that we might be looking at a four-way interaction between eagles, salmon, herring and marine birds. Eventually Butler and Esler’s research will enable us to better manage and ensure the health of these marine wildlife populations.
Your support of the SeaDoc Society makes this work possible.
With thanks,
Kirsten Gilardi & Joe Gaydos
